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Thomas C Weart, Kenneth D Miller, Charles B Simone II Marlene and Stewart Greenebaum Comprehensive Cancer Center, University of Maryland Medical Center, Baltimore, MD, USA Abstract: Advanced non-small-cell lung cancer (NSCLC) remains a challenging disease. The limited utility of chemotherapy indicates the need for additional therapeutic options. Targeted therapy continues to be an important tool in the treatment of NSCLC. Mutations within the RAS–RAF–MEK–MAPK pathway, specifically the BRAF V600E mutation, have become an important target for the subset of NSCLC patients with this mutation. This paper summarizes the clinical evidence that lead to the recent approval of the combination of dabrafenib and trametinib to treat patients with advanced NSCLC who harbor a BRAF V600E mutation. Keywords: BRAF mutation, MEK, NSCLC, lung cancer, dabrafenib, trametinib

Purpose: This study aimed to investigate a dose rate optimization framework based on the spot-scanning patterns to improve ultrahigh-dose-rate coverage of critical organs at risk (OARs) for proton pencil beam scanning (PBS) FLASH radiation therapy (ultrahigh dose-rate (often referred to as >40 Gy per second) delivery) and present implementation of a genetic algorithm (GA) method for spot sequence optimization to achieve PBS FLASH dose rate optimization under relatively low nozzle beam currents., Methods and Materials: First, a multifield FLASH plan was developed to meet all the dosimetric goals and optimal FLASH dose rate coverage by considering the deliverable minimum monitor unit constraint. Then, a GA method was implemented into the in-house treatment platform to maximize the dose rate by exploring the best spot delivery sequence. A phantom study was performed to evaluate the effectiveness of the dose rate optimization. Then, 10 consecutive plans for patients with lung cancer previously treated using PBS intensity-modulated proton therapy were optimized using 45 GyRBE in 3 fractions for both transmission and Bragg peak FLASH radiation therapy for further validation. The spot delivery sequence of each treatment field was optimized using this GA. The ultrahigh-dose-rate-volume histogram and dose rate coverage V 40GyRBE/s were investigated to assess the efficacy of dose rate optimization quantitatively., Results: Using a relatively low monitor unit/spot of 150, corresponding to a nozzle beam current of 65 nA, the FLASH dose rate ratio V 40GyRBE/s of the OAR contour of the core was increased from 0% to ∼60% in the phantom study. In the patients with lung cancer, the ultrahigh-dose-rate coverage V 40GyRBE/s was improved from 15.2%, 15.5%, 17.6%, and 16.0% before the delivery sequence optimization to 31.8%, 43.5%, 47.6%, and 30.5% after delivery sequence optimization in the lungs-GTV (gross tumor volume), spinal cord, esophagus, and heart (for all, P < .001). When the beam current increased to 130 nA, V 40GyRBE/s was improved from 45.1%, 47.1%, 51.2%, and 51.4% to 65.3%, 83.5%, 88.1%, and 69.4% (P < .05). The averaged V 40GyRBE/s for the target and OARs increased from 12.9% to 41.6% and 46.3% to 77.5% for 65 and 130 nA, respectively, showing significant improvements based on a clinical proton system. After optimizing the dose rate for the Bragg peak FLASH technique with a beam current of 340 nA, the V 40GyRBE/s values for the lung GTV, spinal cord, esophagus, and heart were increased by 8.9%, 15.8%, 22%, and 20.8%, respectively., Conclusions: An optimal plan quality can be maintained as the spot delivery sequence optimization is a separate independent process after the plan optimization. Both the phantom and patient results demonstrated that novel spot delivery sequence optimization can effectively improve the ultrahigh-dose-rate coverage for critical OARs, which can potentially be applied in clinical practice for better OARs-sparing efficacy., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The aim of this study is to assess the accuracy of Chat Generative Pretrained Transformer (ChatGPT) in response to oncology examination questions in the setting of one-shot learning. Consecutive national radiation oncology in-service multiple-choice examinations were collected and inputted into ChatGPT 4o and ChatGPT 3.5 to determine ChatGPT's answers. ChatGPT's answers were then compared with the answer keys to determine whether ChatGPT correctly or incorrectly answered each question and to determine if improvements in responses were seen with the newer ChatGPT version. A total of 600 consecutive questions were inputted into ChatGPT. ChatGPT 4o answered 72.2% questions correctly, whereas 3.5 answered 53.8% questions correctly. There was a significant difference in performance by question category (P < .01). ChatGPT performed poorer with respect to knowledge of landmark studies and treatment recommendations and planning. ChatGPT is a promising technology, with the latest version showing marked improvement. Although it still has limitations, with further evolution, it may be considered a reliable resource for medical training and decision making in the oncology space., (Copyright © 2024 American College of Radiology. Published by Elsevier Inc. All rights reserved.)

Background/Objectives: Uveal melanoma is the most common primary intraocular malignancy in adults. Treatment options for localized, early-stage disease include enucleation, brachytherapy, and proton beam therapy. This review aims to evaluate the role of proton therapy in the definitive management of uveal melanoma, focusing on its physics, radiobiology, treatment techniques, and associated outcomes. Methods: This narrative review synthesizes current literature on proton therapy for uveal melanoma, emphasizing case selection, treatment efficacy, and side effects. Results: Proton therapy offers significant advantages for thicker uveal melanomas (over 8 mm) due to its unique physical properties, including a rapid dose fall-off that protects critical structures like the retina and optic nerve. Proton therapy may have benefits in tumor control for ocular melanomas given its increased relative biological effectiveness relative to photon therapy for these typically more radioresistant melanomas. Proton therapy may also hold special value for uveal melanomas in close proximity to the optic nerve, as patients are at high risk of visual toxicities with brachytherapy. The review discusses the efficacy of proton therapy across small, medium, and large tumors, along with strategies for improving patient survival through combined systemic therapy. Additionally, the potential of ocular reirradiation with proton therapy is addressed. Conclusions: Proton therapy is an effective treatment for uveal melanoma. It offers advantages over brachytherapy for large tumors, tumors that are close to the optic nerve or insertion of extra-ocular muscles.

Cancer is the second leading cause of death worldwide. Around half of all cancer patients undergo some type of radiation therapy throughout the course of their treatment. Photon radiation remains (RT) the most widely utilized modality of radiotherapy despite recent advancements in proton radiation therapy (PBT). PBT makes use of the particle's biological property known as the Bragg peak to better spare healthy tissue from radiation damage, with data to support that this treatment modality is less toxic than photon RT. Hence, proton radiation dosimetry looks better compared to photon dosimetry; however, due to proton-specific uncertainties, unexpected acute, subacute, and long-term toxicities can be encountered. Reported neurotoxicity resulting from proton radiation treatments include radiation necrosis, moyamoya syndrome, neurosensory toxicities, brain edema, neuromuscular toxicities, and neurocognitive toxicities. Pulmonary toxicities include pneumonitis and fibrosis, pleural effusions, and bronchial toxicities. Pericarditis, pericardial effusions, and atrial fibrillations are among the cardiac toxicities related to proton therapy. Gastrointestinal and hematological toxicities are also found in the literature. Genitourinary toxicities include urinary and reproductive-related toxicities. Osteological, oral, endocrine, and skin toxicities have also been reported. The side effects will be comparable to the ones following photon RT, nonetheless at an expected lower incidence. The toxicities collected mainly from case reports and clinical trials are described based on the organs affected and functions altered.

Ultrahigh-dose-rate therapy, also known as FLASH radiotherapy (RT), is an emerging technique that is garnering significant interest in cancer treatment due to its potential to revolutionize therapy. This method can achieve comparable tumor control to conventional-dose-rate RT while offering the enhanced protection of normal tissue through the FLASH-sparing effect. This innovative technique has demonstrated promising results in preclinical studies involving animals and cell lines. Particularly noteworthy is its potential application in treating head and neck (HN) cancers, especially in patients with challenging recurrent tumors and reirradiation cases, where the toxicity rates with conventional radiotherapy are high. Such applications aim to enhance tumor control while minimizing side effects and preserving patients' quality of life. In comparison to electron or photon FLASH modalities, proton therapy has demonstrated superior dosimetric and delivery characteristics and is a safe and effective FLASH treatment for human malignancies. Compared to the transmission proton FLASH, single-energy Bragg peak FLASH is a novel delivery method that allows highly conformal doses to targets and minimal radiation doses to crucial OARs. Proton Bragg peak FLASH for HN cancer has still not been well studied. This review highlights the significance of proton FLASH in enhancing cancer therapy by examining the advantages and challenges of using it for HN cancer reirradiation.

Introduction: The multidisciplinary American Radium Society Thoracic Committee was assigned to create appropriate use criteria on cardiac toxicity prevention and management for patients undergoing radiotherapy., Methods: A systematic review of the current literature was conducted. Case variants of patients with thoracic malignancies undergoing radiation were created based on presence or absence of cardiovascular risk factors and treatment-related risks assessed by dose exposure to the heart and cardiac substructures. Modified Delphi methodology was used to evaluate the variants and procedures, with less than or equal to three rating points from median defining agreement/consensus., Results: A total of six variants were evaluated. The panel felt that patients with cardiac comorbidities at high risk for radiation-related cardiac toxicity should undergo a prescreening cardiac-focused history and physical (H&P) examination, electrocardiogram, cardiac imaging including an echocardiogram, and referral to a cardiologist/cardio-oncologist. Recommendations for those without cardiac comorbidities at low risk for cardiac toxicity were to undergo a baseline H&P examination only. Conversely, those without cardiac comorbidities but at high risk for radiation-related cardiac toxicity were recommended to undergo a prescreening electrocardiogram, in addition to a H&P examination. For patients with cardiac comorbidities at low risk for cardiac toxicity, the panel felt that prescreening and postscreening tests may be appropriate., Conclusions: The American Radium Society Thoracic appropriate use criteria panel has developed multidisciplinary consensus guidelines for cardiac toxicity prevention, surveillance, and management after thoracic radiotherapy based on cardiac comorbidities at presentation and risk of radiation-related cardiac toxicity., Competing Interests: Disclosure All panelists were required to declare all conflicts of interest for the previous 36 months before initiating work on this document. These complete disclosure forms are retained by the American Radium Society in perpetuity. The American Radium Society Appropriate Use Criteria Steering Committee reviewed these disclosures with the chair and co-chair of this document and approved participation of the panelists before starting development of this work., (Copyright © 2024 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.)

Purpose: Ultrahigh dose-rate FLASH radiation therapy has emerged as a modality that promises to reduce normal tissue toxicity while maintaining tumor control. Previous studies of gastrointestinal toxicity using passively scattered FLASH proton therapy (PRT) have, however, yielded mixed results, suggesting that the requirements for gastrointestinal sparing by FLASH are an open question. Furthermore, the more clinically relevant pencil beam scanned (PBS) FLASH PRT has not yet been assessed in this context, despite differences in the spatiotemporal dose-rate distributions compared with passively scattered PRT. Here, to our knowledge, we provide the first report on the effects of PBS FLASH PRT on acute gastrointestinal injury in mice after whole abdominal irradiation., Methods and Materials: Whole abdominal irradiation was performed on C57BL/6J mice using the entrance channel of the Bragg curve of a 250 MeV PBS proton beam at field-averaged dose rates of 0.6 Gy/s for conventional (CONV) and 80 to 100 Gy/s for FLASH PRT. A 2D strip ionization chamber array was used to measure the dose and dose rate for each mouse. Survival was assessed at 14 Gy. Intestines were harvested and processed as Swiss rolls for analysis using a novel artificial intelligence-based crypt assay to quantify crypt regeneration 4 days after irradiation., Results: Survival was significantly reduced after 14 Gy FLASH PRT compared with CONV (P < .001). Our artificial intelligence-based crypt assays demonstrated no significant difference in intestinal crypts/cm or crypt depth between groups 4 days after irradiation. Furthermore, we found no significant difference in 5-ethynyl-2'-deoxyuridine + cells/crypt or Olfactomedin4 + intestinal stem cells with FLASH relative to CONV PRT., Conclusions: Overall, our data demonstrate significantly impaired survival after abdominal PBS FLASH PRT without apparent differences in intestinal histology 4 days after irradiation., (Copyright © 2024. Published by Elsevier Inc.)

Introduction: Definitive radiation therapy is considered standard therapy for medically inoperable early-stage NSCLC. Nevertheless, for patients with tumors located near structures such as the proximal tracheobronchial tree, esophagus, heart, spinal cord, and brachial plexus, the optimal management regimen is controversial. The objective was to develop expert multidisciplinary consensus guidelines on managing medically inoperable NSCLC located in a central or ultracentral location relative to critical organs at risk., Methods: Case variants regarding centrally and ultracentrally located lung tumors were developed by the 15-member multidisciplinary American Radium Society (ARS) Thoracic Appropriate Use Criteria (AUC) expert panel. A comprehensive review of the English medical literature was performed from January 1 1946 to December 31 2023 to inform consensus guidelines. Modified Delphi methods were used by the panel to evaluate the variants and procedures, with at least three rating points from median defining agreement/consensus. The guideline was then approved by the ARS Executive Committee and released for public comment per established ARS procedures., Results: The Thoracic ARS AUC Panel identified 90 relevant references and obtained consensus in all variants. Radiotherapy alone was considered appropriate, with additional immunotherapy to be considered primarily in the clinical trial setting. Hypofractionated radiotherapy in eight to 18 fractions was considered appropriate for ultracentral lesions near the proximal tracheobronchial tree, upper trachea, and esophagus. For other ultracentral lesions near the heart, great vessels, brachial plexus, and spine, or for non-ultracentral but still central lesions, five-fraction stereotactic body radiation therapy was also considered an appropriate option. Intensity-modulated radiotherapy was considered appropriate and three-dimensional-conformal radiotherapy inappropriate for all variants. Other treatment planning techniques to decrease the risk of overdosing critical organs at risk were also considered., Conclusions: The ARS Thoracic AUC panel has developed multidisciplinary consensus guidelines for various presentations of stage I NSCLC in a central or ultracentral location., Competing Interests: Disclosure Dr. Park reported personal fees AstraZeneca, Bristol-Myers Squibb, Daichii Sankyo, G1 Therapeutics, Galera Medical, RefleXion Medical, Regeneron, and research funding from Merck Sharp & Dohme. Dr. Rimner reported grants from Varian Medical Systems, AstraZeneca, Merck, Boehringer Ingelheim, Pfizer, and National Institutes of Health and personal fees from AstraZeneca, Merck, and MoreHealth. Dr. Chang reported grants from Bristol Myers Squibb and personal fees from Varian Medical Systems and IBA. Dr. Chun reported personal fees from AstraZeneca, Norton Healthcare, Binaytara Foundation, ViewRay, Japanese Society for Radiation Oncology, Hong Kong Precision Oncology Society, and Curio Science. Dr. Donington reported personal fees from Amgen, AstraZeneca, Bristol-Myers Squibb, Merck, and Roche/Genentech. Dr. Edelman reported personal fees from AstraZeneca, Takeda, Glaxo Smith Kline, Omega Therapeutics, Novocure, InterVenn, WindMil, Seattle Genetics, Regeneron/Sanofi, Flame Consulting, Proventus Consulting, GE Healthcare Consulting, BioAlta Consulting, Replimmune Consulting, Coherus Consulting, and AnHeart. Dr. Gubens reported personal fees from AnHeart, AstraZeneca, Atreca, Bristol-Myers Squibb, Cardinal Health, Genzyme, Genentech/Roche, Gilead, Guardant, Invitae, iTeos, Merus, Sanofi, Summit, and Surface and grants from Amgen, JNJ, Merck, OncoMed, and Trizell. Dr. Higgins reported grants from Jazz Pharmaceuticals and other support from AstraZeneca, Janssen Pharmaceuticals, and RefleXion Medical. Dr. Iyengar reported other support from Incyte and AstraZeneca. Dr. Movsas reported grants from Varian Research, Philips Research, and ViewRay Research. The remaining authors declare no conflict of interest., (Copyright © 2024 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.)

Purpose: To investigate quality assurance (QA) techniques for in vivo dosimetry and establish its routine uses for proton FLASH small animal experiments with a saturated monitor chamber., Methods and Materials: 227 mice were irradiated at FLASH or conventional (CONV) dose rates with a 250 MeV FLASH-capable proton beamline using pencil beam scanning to characterize the proton FLASH effect on abdominal irradiation and examining various endpoints. A 2D strip ionization chamber array (SICA) detector was positioned upstream of collimation and used for in vivo dose monitoring during irradiation. Before each irradiation series, SICA signal was correlated with the isocenter dose at each delivered dose rate. Dose, dose rate, and 2D dose distribution for each mouse were monitored with the SICA detector., Results: Calibration curves between the upstream SICA detector signal and the delivered dose at isocenter had good linearity with minimal R 2 values of 0.991 (FLASH) and 0.985 (CONV), and slopes were consistent for each modality. After reassigning mice, standard deviations were less than 1.85 % (FLASH) and 0.83 % (CONV) for all dose levels, with no individual subject dose falling outside a ± 3.6 % range of the designated dose. FLASH fields had a field-averaged dose rate of 79.0 ± 0.8 Gy/s and mean local average dose rate of 160.6 ± 3.0 Gy/s. In vivo dosimetry allowed for the accurate detection of variation between the delivered and the planned dose., Conclusion: In vivo dosimetry benefits FLASH experiments through enabling real-time dose and dose rate monitoring allowing mouse cohort regrouping when beam fluctuation causes delivered dose to vary from planned dose., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Quality assurance (QA) for ultra-high dose rate (UHDR) irradiation is a crucial aspect in the emerging field of FLASH radiotherapy (FLASH-RT). This innovative treatment approach delivers radiation at UHDR, demanding careful adoption of QA protocols and procedures. A comprehensive understanding of beam properties and dosimetry consistency is vital to ensure the safe and effective delivery of FLASH-RT., Purpose: To develop a comprehensive pre-treatment QA program for cyclotron-based proton pencil beam scanning (PBS) FLASH-RT. Establish appropriate tolerances for QA items based on this study's outcomes and TG-224 recommendations., Methods: A 250 MeV proton spot pattern was designed and implemented using UHDR with a 215nA nozzle beam current. The QA pattern that covers a central uniform field area, various spot spacings, spot delivery modes and scanning directions, and enabling the assessment of absolute, relative and temporal dosimetry QA parameters. A strip ionization chamber array (SICA) and an Advanced Markus chamber were utilized in conjunction with a 2 cm polyethylene slab and a range (R 80 ) verification wedge. The data have been monitored for over 3 months., Results: The relative dosimetries were compliant with TG-224. The variations of temporal dosimetry for scanning speed, spot dwell time, and spot transition time were within ± 1 mm/ms, ± 0.2 ms, and ± 0.2 ms, respectively. While the beam-to-beam absolute output on the same day reached up to 2.14%, the day-to-day variation was as high as 9.69%. High correlation between the absolute dose and dose rate fluctuations were identified. The dose rate of the central 5 × 5 cm 2 field exhibited variations within 5% of the baseline value (155 Gy/s) during an experimental session., Conclusions: A comprehensive QA program for FLASH-RT was developed and effectively assesses the performance of a UHDR delivery system. Establishing tolerances to unify standards and offering direction for future advancements in the evolving FLASH-RT field., (© 2024 The Author(s). Journal of Applied Clinical Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.)

This position paper, led by the NRG Oncology Particle Therapy Work Group, focuses on the concept of relative biologic effect (RBE) in clinical proton therapy (PT), with the goal of providing recommendations for the next-generation clinical trials with PT on the best practice of investigating and using RBE, which could deviate from the current standard proton RBE value of 1.1 relative to photons. In part 1, current clinical utilization and practice are reviewed, giving the context and history of RBE. Evidence for variation in RBE is presented along with the concept of linear energy transfer (LET). The intertwined nature of tumor radiobiology, normal tissue constraints, and treatment planning with LET and RBE considerations is then reviewed. Part 2 summarizes current and past clinical data and then suggests the next steps to explore and employ tools for improved dynamic models for RBE. In part 3, approaches and methods for the next generation of prospective clinical trials are explored, with the goal of optimizing RBE to be both more reflective of clinical reality and also deployable in trials to allow clinical validation and interpatient comparisons. These concepts provide the foundation for personalized biologic treatments reviewed in part 4. Finally, we conclude with a summary including short- and long-term scientific focus points for clinical PT. The practicalities and capacity to use RBE in treatment planning are reviewed and considered with more biological data in hand. The intermediate step of LET optimization is summarized and proposed as a potential bridge to the ultimate goal of case-specific RBE planning that can be achieved as a hypothesis-generating tool in near-term proton trials., (Published by Elsevier Inc.)

Purpose: The National Association for Proton Therapy conducted 8 surveys of all operational United States proton centers (2012-2021) and analyzed the patients treated, diagnoses, and treatment complexity to evaluate trends and diversification of patients receiving proton therapy., Methods and Materials: Detailed surveys were sent in 2015, which requested data from 2012 to 2014, and then annually thereafter to active proton centers in the United States. The numbers of patient treated at each center for the preceding calendar year(s) were collated for tumors in the following categories: central nervous system, intraocular, pituitary, skull base/skeleton, head/neck, lung, retroperitoneal/soft tissue sarcoma, pediatric (solid tumors in children of age ≤18), gastrointestinal tract, urinary tract, female pelvic, prostate, breast, and "other." Complexity levels were assessed using Current Procedural Terminology codes 77520-77525., Results: Survey response rates were excellent (100% in 2015 to 94.9% in 2021); additional publicly available information provided near-complete information on all centers. Trend comparisons between 2012 and 2021 showed that the total annual number of patients treated with protons gradually increased from 5377 to 15,829. The largest numeric increases were for head/neck (316 to 2303; 7.3-fold), breast (93 to 1452; 15.6-fold), and gastrointestinal tumors (170 to 1259; 7.4-fold). Patient numbers also increased significantly for central nervous system (598 to 1743; 2.9-fold), pediatric (685 to 1870; 2.7-fold), and skull base tumors (179 to 514; 2.9-fold). For prostate cancer, the percentage of proton-treated patients decreased from 43.4% to 25.0% of the total. Simple compensated treatments decreased from 43% in 2012 to 7% in 2021, whereas intermediate complexity treatments increased from 45% to 73%., Conclusions: The number of patients treated with protons is gradually increasing, with a substantial proportionate decline in patients with prostate cancer receiving proton therapy. The number of patients treated for "commonly accepted" indications for protons (eg, pediatric, central nervous system, and skull base tumors) is gradually increasing. Greater proportional increases were observed for breast, lung, head/neck, and gastrointestinal tumors. Treatment complexity is gradually increasing over time., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Stereotactic body radiation therapy (SBRT) and hypofractionation using pencil-beam scanning (PBS) proton therapy (PBSPT) is an attractive option for thoracic malignancies. Combining the advantages of target coverage conformity and critical organ sparing from both PBSPT and SBRT, this new delivery technique has great potential to improve the therapeutic ratio, particularly for tumors near critical organs. Safe and effective implementation of PBSPT SBRT/hypofractionation to treat thoracic malignancies is more challenging than the conventionally fractionated PBSPT because of concerns of amplified uncertainties at the larger dose per fraction. The NRG Oncology and Particle Therapy Cooperative Group Thoracic Subcommittee surveyed proton centers in the United States to identify practice patterns of thoracic PBSPT SBRT/hypofractionation. From these patterns, we present recommendations for future technical development of proton SBRT/hypofractionation for thoracic treatment. Among other points, the recommendations highlight the need for volumetric image guidance and multiple computed tomography-based robust optimization and robustness tools to minimize further the effect of uncertainties associated with respiratory motion. Advances in direct motion analysis techniques are urgently needed to supplement current motion management techniques., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Because of improved survival of cancer patients, more patients irradiated for brain metastases develop intracerebral recurrences requiring subsequent courses of radiotherapy. Five studies focused on reirradiation with whole-brain radiation therapy (WBRT) after initial WBRT for brain metastases. Following the second WBRT course, improvement of clinical symptoms was found in 31-68% of patients. Rates of neurotoxicity, such as encephalopathy or cognitive decline, were reported in two studies (1.4% and 32%). In another study, severe or unexpected adverse events were not observed. Survival following the second WBRT course was generally poor, with median survival times of 2.9-4.1 months. The survival prognosis of patients receiving two courses of WBRT can be estimated by a scoring tool considering five prognostic factors. Three studies investigated reirradiation with single-fraction stereotactic radiosurgery (SF-SRS) following primary WBRT. One-year local control rates were 74-91%, and median survival times ranged between 7.8 and 14 months. Rates of radiation necrosis (RN) after reirradiation were 0-6%. Seven studies were considered that investigated re-treatment with SF-SRS or fractionated stereotactic radiation therapy (FSRT) following initial SF-SRS or FSRT. One-year local control rates were 60-88%, and the median survival times ranged between 8.3 and 25 months. During follow-up after reirradiation, rates of overall (asymptomatic or symptomatic) RN ranged between 12.5% and 30.4%. Symptomatic RN occurred in 4.3% to 23.9% of cases (patients or lesions). The risk of RN associated with symptoms and/or requiring surgery or corticosteroids appears lower after reirradiation with FSRT when compared to SF-SRS. Other potential risk factors of RN include the volume of overlap of normal tissue receiving 12 Gy at the first course and 18 Gy at the second course of SF-SRS, maximum doses ≥40 Gy of the first or the second SF-SRS courses, V12 Gy >9 cm3 of the second course, initial treatment with SF-SRS, volume of normal brain receiving 5 Gy during reirradiation with FSRT, and systemic treatment. Cumulative EQD2 ≤100-120 Gy2 to brain, <100 Gy2 to brainstem, and <75 Gy2 to chiasm and optic nerves may be considered safe. Since most studies were retrospective in nature, prospective trials are required to better define safety and efficacy of reirradiation for recurrent or progressive brain metastases.

An increasing number of patients irradiated for metastatic epidural spinal cord compression (MESCC) experience an in-field recurrence and require a second course of radiotherapy. Reirradiation can be performed with conventional radiotherapy or highly-conformal techniques such as intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), and stereotactic body radiation therapy (SBRT). When using conventional radiotherapy, a cumulative biologically effective dose (BED) ≤120 calculated with an α/β value of 2 Gy (Gy2) was not associated with radiation myelopathy in a retrospective study of 124 patients and is considered safe. In that study, conventional reirradiation led to improvements of motor deficits in 36% of patients and stopped further symptomatic progression in another 50% (overall response 86%). In four other studies, overall response rates were 82-89%. In addition to the cumulative BED or equivalent dose in 2 Gy fractions (EQD2), the interval between both radiotherapy courses <6 months and a BED per course ≥102 Gy2 (corresponding to an EQD2 ≥51 Gy2) were identified as risk factors for radiation myelopathy. Without these risk factors, a BED >120 Gy2 may be possible. Scoring tools have been developed that can assist physicians in estimating the risk of radiation myelopathy and selecting the appropriate dose-fractionation regimen of re-treatment. Reirradiation of MESCC may also be performed with highly-conformal radiotherapy. With IMRT or VMAT, rates of pain relief and improvement of neurologic symptoms of 60-93.5% and 42-73%, respectively, were achieved. One-year local control rates ranged between 55% and 88%. Rates of myelopathy or radiculopathy and vertebral compression fractures were 0% and 0-9.3%, respectively. With SBRT, rates of pain relief were 65-86%. Two studies reported improvements in neurologic symptoms of 0% and 82%, respectively. One-year local control rates were 74-83%. Rates of myelopathy or radiculopathy and vertebral compression fractures were 0-4.5% and 4.5-13.8%, respectively. For SBRT, a cumulative maximum EQD2 to thecal sac ≤70 Gy2, a maximum EQD2 of SBRT ≤25 Gy2, a ratio ≤0.5 of thecal sac maximum EQD2 of SBRT to maximum cumulative EQD2, and an interval between both courses ≥5 months were associated with a lower risk of myelopathy. Additional prospective trials are required to better define the options of reirradiation of MESCC.

Bone metastases are a common and debilitating consequence of advanced cancer, often necessitating palliative radiation therapy (RT) for pain relief. Reirradiation (reRT) of bone metastases is often considered after lack of pain relief following an initial course of RT, after a partial but unsatisfying pain response to an initial course of radiotherapy, or after pain recurrence following a complete or partial pain response to an initial course of RT. The NCIC CTG SC.20 trial, a landmark multicenter, randomized, non-blinded, controlled non-inferiority trial, addressed the critical question of optimal dose fractionation for reRT in this patient population. This trial compared the efficacy and toxicity of a single 8 Gy fraction to multiple fractions totaling 20 Gy in 850 patients with painful bone metastases requiring reRT. The primary endpoint was overall pain response at 2 months, with secondary endpoints of quality of life (QoL) measures, functional interference, and toxicity profiles assessed using patient-reported questionnaires and the European Organisation for Research and Treatment of Cancer (EORTC) QLQ-C30. The intention-to-treat analysis revealed no significant difference in pain response between the two arms, meeting the pre-specified non-inferiority criteria. The per-protocol analysis suggested a potential benefit for a subset of patients receiving multiple fractions, although this was not statistically robust. Acute toxicities were more prevalent in the multiple fractions arm, with implications for patient comfort and healthcare utilization. Importantly, responders to reRT reported significant improvements in functional interference and QoL. The trial's findings support the use of a patient-centric approach to palliative RT, highlighting the viability of a single 8 Gy fraction as a less toxic and more convenient treatment option, albeit with consideration for individual patient circumstances. These results have significant implications for clinical practice, potentially reducing healthcare burdens while optimizing patient convenience during palliative care for painful bone metastases.

Purpose: Larger tumors are underrepresented in most prospective trials on stereotactic body radiation therapy (SBRT) for inoperable non-small cell lung cancer (NSCLC). We performed this phase 1 trial to specifically study the maximum tolerated dose (MTD) of SBRT for NSCLC >3 cm., Methods and Materials: A 3 + 3 dose-escalation design (cohort A) with an expansion cohort at the MTD (cohort B) was used. Patients with inoperable NSCLC >3 cm (T2-4) were eligible. Select ipsilateral hilar and single-station mediastinal nodes were permitted. The initial SBRT dose was 40 Gy in 5 fractions, with planned escalation to 50 and 60 Gy in 5 fractions. Adjuvant chemotherapy was mandatory for cohort A and optional for cohort B, but no patients in cohort B received chemotherapy. The primary endpoint was SBRT-related acute grade (G) 4+ or persistent G3 toxicities (Common Terminology Criteria for Adverse Events version 4.03). Secondary endpoints included local failure (LF), distant metastases, disease progression, and overall survival., Results: The median age was 80 years; tumor size was >3 cm and ≤5 cm in 20 (59%) and >5 cm in 14 patients (41%). In cohort A (n = 9), 3 patients treated to 50 Gy experienced G3 radiation pneumonitis (RP), thus defining the MTD. In the larger dose-expansion cohort B (n = 25), no radiation therapy-related G4+ toxicities and no G3 RP occurred; only 2 patients experienced G2 RP. The 2-year cumulative incidence of LF was 20.2%, distant failure was 34.7%, and disease progression was 54.4%. Two-year overall survival was 53%. A biologically effective dose (BED) <100 Gy was associated with higher LF (P = .006); advanced stage and higher neutrophil/lymphocyte ratio were associated with greater disease progression (both P = .004)., Conclusions: Fifty Gy in 5 fractions is the MTD for SBRT to tumors >3 cm. A higher BED is associated with fewer LFs even in larger tumors. Cohort B appears to have had less toxicity, possibly due to the omission of chemotherapy., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Purpose: The recently proposed Integrated Physical Optimization Intensity Modulated Proton Therapy (IPO-IMPT) framework allows simultaneous optimization of dose, dose rate, and linear energy transfer (LET) for ultra-high dose rate (FLASH) treatment planning. Finding solutions to IPO-IMPT is difficult because of computational intensiveness. Nevertheless, an inverse solution that simultaneously specifies the geometry of a sparse filter and weights of a proton intensity map is desirable for both clinical and preclinical applications. Such solutions can reduce effective biologic dose to organs at risk in patients with cancer as well as reduce the number of animal irradiations needed to derive extra biologic dose models in preclinical studies., Methods and Materials: Unlike the initial forward heuristic, this inverse IPO-IMPT solution includes simultaneous optimization of sparse range compensation, sparse range modulation, and spot intensity. The daunting computational tasks vital to this endeavor were resolved iteratively with a distributed computing framework to enable Simultaneous Intensity and Energy Modulation and Compensation (SIEMAC). SIEMAC was demonstrated on a human patient with central lung cancer and a minipig., Results: SIEMAC simultaneously improves maps of spot intensities and patient-field-specific sparse range compensators and range modulators. For the patient with lung cancer, at our maximum nozzle current of 300 nA, dose rate coverage above 100 Gy/s increased from 57% to 96% in the lung and from 93% to 100% in the heart, and LET coverage above 4 keV/µm dropped from 68% to 9% in the lung and from 26% to <1% in the heart. For a simple minipig plan, the full-width half-maximum of the dose, dose rate, and LET distributions decreased by 30%, 1.6%, and 57%, respectively, again with similar target dose coverage, thus reducing uncertainty in these quantities for preclinical studies., Conclusions: The inverse solution to IPO-IMPT demonstrated the capability to simultaneously modulate subspot proton energy and intensity distributions for clinical and preclinical studies., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Importance: The treatment of locally advanced non-small cell lung cancer (LA-NSCLC) has been informed by more than 5 decades of clinical trials and other relevant literature. However, controversies remain regarding the application of various radiation and systemic therapies in commonly encountered clinical scenarios., Objective: To develop case-referenced consensus and evidence-based guidelines to inform clinical practice in unresectable LA-NSCLC., Evidence Review: The American Radium Society (ARS) Appropriate Use Criteria (AUC) Thoracic Committee guideline is an evidence-based consensus document assessing various clinical scenarios associated with LA-NSCLC. A systematic review of the literature with evidence ratings was conducted to inform the appropriateness of treatment recommendations by the ARS AUC Thoracic Committee for the management of unresectable LA-NSCLC., Findings: Treatment appropriateness of a variety of LA-NSCLC scenarios was assessed by a consensus-based modified Delphi approach using a range of 3 points to 9 points to denote consensus agreement. Committee recommendations were vetted by the ARS AUC Executive Committee and a 2-week public comment period before official approval and adoption. Standard of care management of good prognosis LA-NSCLC consists of combined concurrent radical (60-70 Gy) platinum-based chemoradiation followed by consolidation durvalumab immunotherapy (for patients without progression). Planning and delivery of locally advanced lung cancer radiotherapy usually should be performed using intensity-modulated radiotherapy techniques. A variety of palliative and radical fractionation schedules are available to treat patients with poor performance and/or pulmonary status. The salvage therapy for a local recurrence after successful primary management is complex and likely requires both multidisciplinary input and shared decision-making with the patient., Conclusions and Relevance: Evidence-based guidance on the management of various unresectable LA-NSCLC scenarios is provided by the ARS AUC to optimize multidisciplinary patient care for this challenging patient population.

Introduction: It was hypothesized that use of proton beam therapy (PBT) in patients with locally advanced non-small cell lung cancer treated with concurrent chemoradiation and consolidative immune checkpoint inhibition is associated with fewer unplanned hospitalizations compared with intensity-modulated radiotherapy (IMRT)., Methods: Patients with locally advanced non-small cell lung cancer treated between October 2017 and December 2021 with concurrent chemoradiation with either IMRT or PBT ± consolidative immune checkpoint inhibition were retrospectively identified. Logistic regression was used to assess the association of radiation therapy technique with 90-day hospitalization and grade 3 (G3+) lymphopenia. Competing risk regression was used to compare G3+ pneumonitis, G3+ esophagitis, and G3+ cardiac events. Kaplan-Meier method was used for progression-free survival and overall survival. Inverse probability treatment weighting was applied to adjust for differences in PBT and IMRT groups., Results: Of 316 patients, 117 (37%) received PBT and 199 (63%) received IMRT. The PBT group was older (p < .001) and had higher Charlson Comorbidity Index scores (p = .02). The PBT group received a lower mean heart dose (p < .0001), left anterior descending artery V15 Gy (p = .001), mean lung dose (p = .008), and effective dose to immune circulating cells (p < .001). On inverse probability treatment weighting analysis, PBT was associated with fewer unplanned hospitalizations (adjusted odds ratio, 0.55; 95% CI, 0.38-0.81; p = .002) and less G3+ lymphopenia (adjusted odds ratio, 0.55; 95% CI, 0.37-0.81; p = .003). There was no difference in other G3+ toxicities, progression-free survival, or overall survival., Conclusions: PBT is associated with fewer unplanned hospitalizations, lower effective dose to immune circulating cells and less G3+ lymphopenia compared with IMRT. Minimizing dose to lymphocytes may be warranted, but prospective data are needed., (© 2024 American Cancer Society.)

Background: Patients treated for lung cancer (LC) often experience locoregional failure after initial treatment. Due to technological advances, thoracic reirradiation (re-RT) has become a viable treatment option. We sought to investigate the use of thoracic re-RT in LC patients over a time period characterized by technological advances in a large, multi-center cohort., Methods and Materials: LC patients treated with thoracic re-RT in two University Hospitals from 2010-2020 were identified. Clinical variables and RT data were extracted from the medical records and treatment planning systems. Overall survival (OS) was calculated from the last day of re-RT until death or last follow up., Results: 296 patients (small cell LC n=30, non-small cell LC n=266) were included. Three-dimensional conformal radiation therapy was the RT technique used most frequently (63%), and 86% of all patients were referred for re-RT with palliative treatment intent. During the second half of the study period, the use of thoracic re-RT increased in general, more patients received curative re-RT, and there was an increased use of stereotactic body radiation therapy (SBRT). Median time between initial RT and re-RT was 18 months (range 1-213 months). Only 83/296 patients had combined treatment plans that allowed for registration of combined doses to organs at risk (OAR). Most of the combined doses to OAR were below recommendations from guidelines. Multivariate analysis showed superior OS (p<0.05) in patients treated with curative intent, SBRT or intensity modulated radiation therapy or had excellent performance status prior to re-RT., Conclusions: The use of re-RT increased in the second half of the study period, although 2020 did not follow the trend. The use of SBRT and IMRT became more frequent over the years, yet the majority received palliative re-RT. Combined dose plans were only created for one third of the patients., (Copyright © 2024. Published by Elsevier Inc.)

Background: Accurate, reliable, non-invasive assessment of patients diagnosed with prostate cancer is essential for proper disease management. Quantitative assessment of multi-parametric MRI, such as through artificial intelligence or spectral/statistical approaches, can provide a non-invasive objective determination of the prostate tumor aggressiveness without side effects or potential poor sampling from needle biopsy or overdiagnosis from prostate serum antigen measurements. To simplify and expedite prostate tumor evaluation, this study examined the efficacy of autonomously extracting tumor spectral signatures for spectral/statistical algorithms for spatially registered bi-parametric MRI., Methods: Spatially registered hypercubes were digitally constructed by resizing, translating, and cropping from the image sequences (Apparent Diffusion Coefficient (ADC), High B-value, T2) from 42 consecutive patients in the bi-parametric MRI PI-CAI dataset. Prostate cancer blobs exceeded a threshold applied to the registered set from normalizing the registered set into an image that maximizes High B-value, but minimizes the ADC and T2 images, appearing "green" in the color composite. Clinically significant blobs were selected based on size, average normalized green value, sliding window statistics within a blob, and position within the hypercube. The center of mass and maximized sliding window statistics within the blobs identified voxels associated with tumor signatures. We used correlation coefficients (R) and p -values, to evaluate the linear regression fits of the z-score and SCR (with processed covariance matrix) to tumor aggressiveness, as well as Area Under the Curves (AUC) for Receiver Operator Curves (ROC) from logistic probability fits to clinically significant prostate cancer., Results: The highest R (R > 0.45), AUC (>0.90), and lowest p -values (<0.01) were achieved using z-score and modified registration applied to the covariance matrix and tumor signatures selected from the "greenest" parts from the selected blob., Conclusions: The first autonomous tumor signature applied to spatially registered bi-parametric MRI shows promise for determining prostate tumor aggressiveness.

Purpose: This study aimed to predict the probability of grade ≥2 pneumonitis or dyspnea within 12 months of receiving conventionally fractionated or mildly hypofractionated proton beam therapy for locally advanced lung cancer using machine learning., Methods and Materials: Demographic and treatment characteristics were analyzed for 965 consecutive patients treated for lung cancer with conventionally fractionated or mildly hypofractionated (2.2-3 Gy/fraction) proton beam therapy across 12 institutions. Three machine learning models (gradient boosting, additive tree, and logistic regression with lasso regularization) were implemented to predict Common Terminology Criteria for Adverse Events version 4 grade ≥2 pulmonary toxicities using double 10-fold cross-validation for parameter hyper-tuning without leak of information. Balanced accuracy and area under the curve were calculated, and 95% confidence intervals were obtained using bootstrap sampling., Results: The median age of the patients was 70 years (range, 20-97), and they had predominantly stage IIIA or IIIB disease. They received a median dose of 60 Gy in 2 Gy/fraction, and 46.4% received concurrent chemotherapy. In total, 250 (25.9%) had grade ≥2 pulmonary toxicity. The probability of pulmonary toxicity was 0.08 for patients treated with pencil beam scanning and 0.34 for those treated with other techniques (P = 8.97e-13). Use of abdominal compression and breath hold were highly significant predictors of less toxicity (P = 2.88e-08). Higher total radiation delivered dose (P = .0182) and higher average dose to the ipsilateral lung (P = .0035) increased the likelihood of pulmonary toxicities. The gradient boosting model performed the best of the models tested, and when demographic and dosimetric features were combined, the area under the curve and balanced accuracy were 0.75 ± 0.02 and 0.67 ± 0.02, respectively. After analyzing performance versus the number of data points used for training, we observed that accuracy was limited by the number of observations., Conclusions: In the largest analysis of prospectively enrolled patients with lung cancer assessing pulmonary toxicities from proton therapy to date, advanced machine learning methods revealed that pencil beam scanning, abdominal compression, and lower normal lung doses can lead to significantly lower probability of developing grade ≥2 pneumonitis or dyspnea., (Published by Elsevier Inc.)

Background: Stereotactic ablative radiation therapy (SBRT) is an emerging treatment option for primary renal cell carcinoma (RCC), particularly in patients who are unsuitable for surgery. The aim of this review is to assess the effect of increasing the biologically equivalent dose (BED) via various radiation fractionation regimens on clinical outcomes., Methods: A literature search was conducted in PubMed (Medline), EMBASE, and the Cochrane Library for studies published up to October 2023. Studies reporting on patients with localized RCC receiving SBRT were included to determine its effectiveness on local control, progression-free survival, and overall survival. A random effects model was used to meta-regress clinical outcomes relative to the BED for each study and heterogeneity was assessed by I 2 ., Results: A total of 724 patients with RCC from 22 studies were included, with a mean age of 72.7 years (range: 44.0-81.0). Local control was excellent with an estimate of 99 % (95 %CI: 97-100 %, I 2  = 19 %), 98 % (95 %CI: 96-99 %, I 2  = 8 %), and 94 % (95 %CI: 90-97 %, I 2  = 11 %) at one year, two years, and five years respectively. No definitive association between increasing BED and local control, progression-free survival and overall survival was observed. No publication bias was observed., Conclusions: A significant dose response relationship between oncological outcomes and was not identified, and excellent local control outcomes were observed at the full range of doses. Until new evidence points otherwise, we support current recommendations against routine dose escalation beyond 25-26 Gy in one fraction or 42-48 Gy in three fractions, and to consider de-escalation or compromising target coverage if required to achieve safe organ at risk doses., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: RG: institutional grant funding- Astellas, TerSera. Honoraria: Bayer, Tolmar, Knight, TerSera. SR: Institutional grant funding – Astra Zeneca, Knight therapeutics. Honoraria – Bayer, Astra Zeneca, Tersera, Sanofi, Verity pharma., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Superior vena cava (SVC) syndrome occurs due to obstructed blood flow through the SVC. It can present clinically on a spectrum, between asymptomatic and life-threatening emergency. Patients commonly report a feeling of fullness in the head, facial, neck and upper extremity edema, and dyspnea. On imaging, patients commonly have superior mediastinal widening and pleural effusion. The majority of cases are due to malignant causes, with non-small cell lung cancer, small cell lung cancer, and lymphoma the most commonly associated malignancies. When evaluating patients, a complete staging workup is recommended, as it will determine whether treatment should be definitive/curative or palliative in intent. If the patient requires urgent treatment of venous obstruction, such as in the cases of acute central airway obstruction, severe laryngeal edema and/or coma from cerebral edema, direct opening of the occlusion by endovascular stenting and angioplasty with thrombolysis should be considered. Such an approach can provide immediate relief of symptoms before cancer-specific therapies are initiated. The intent of treatment is to manage the underlying disease while palliating symptoms. Treatment approaches most commonly employ chemotherapy and/or radiation therapy depending on the primary histology. Mildly hypofractionated radiation regimens are most commonly employed and achieve high rates of symptomatic responses generally within 2 weeks of initiating therapy.

Purpose: Reirradiation (reRT) with proton beam therapy (PBT) may offer a chance of cure while minimizing toxicity for patients with isolated intrathoracic recurrences of non-small cell lung cancer (NSCLC). However, distant failure remains common, necessitating strategies to integrate more effective systemic therapy., Methods and Materials: This was a phase 2, single-arm trial (NCT03087760) of consolidation pembrolizumab after PBT reRT for locoregional recurrences of NSCLC. Four to 12 weeks after completion of 60 to 70 Gy PBT reRT, patients without progressive disease received pembrolizumab for up to 12 months. Primary endpoint was progression-free survival (PFS), measured from the start of reRT. Secondary endpoints were overall survival (OS) and National Cancer Institute Common Terminology Criteria for Adverse Events, version 5.0 toxicity., Results: Between 2017 and 2021, 22 patients received PBT reRT. Median interval from prior radiation end to reRT start was 20 months. Most recurrences (91%) were centrally located. Most patients received concurrent chemotherapy (95%) and pencil beam scanning PBT (77%), and 36% had received prior durvalumab. Fifteen patients (68%) initiated consolidation pembrolizumab on trial and received a median of 3 cycles (range, 2-17). Pembrolizumab was discontinued most commonly due to toxicity (n = 5; 2 were pembrolizumab-related), disease progression (n = 4), and completion of 1 year (n = 3). Median follow-up was 38.7 months. Median PFS and OS were 8.8 months (95% CI, 4.2-23.7) and 22.8 months (95% CI, 6.9-not reached), respectively. There was only one isolated in-field failure after reRT. Grade ≥3 toxicities occurred in 10 patients (45%); 2 were pembrolizumab-related. There were 2 grade 5 toxicities, an aorto-esophageal fistula at 6.9 months and hemoptysis at 46.8 months, both probably from reRT. The trial closed early due to widespread adoption of immunotherapy off-protocol., Conclusions: In the first-ever prospective trial combining PBT reRT with consolidation immunotherapy, PFS was acceptable and OS favorable. Late grade 5 toxicity occurred in 2 of 22 patients. This approach may be considered in selected patients with isolated thoracic recurrences of NSCLC., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Purpose: Radiotherapy delivery in the definitive management of lower gastrointestinal (LGI) tract malignancies is associated with substantial risk of acute and late gastrointestinal (GI), genitourinary, dermatologic, and hematologic toxicities. Advanced radiation therapy techniques such as proton beam therapy (PBT) offer optimal dosimetric sparing of critical organs at risk, achieving a more favorable therapeutic ratio compared with photon therapy., Materials and Methods: The international Particle Therapy Cooperative Group GI Subcommittee conducted a systematic literature review, from which consensus recommendations were developed on the application of PBT for LGI malignancies., Results: Eleven recommendations on clinical indications for which PBT should be considered are presented with supporting literature, and each recommendation was assessed for level of evidence and strength of recommendation. Detailed technical guidelines pertaining to simulation, treatment planning and delivery, and image guidance are also provided., Conclusion: PBT may be of significant value in select patients with LGI malignancies. Additional clinical data are needed to further elucidate the potential benefits of PBT for patients with anal cancer and rectal cancer., (© 2024 The Authors.)

Purpose: This practice parameter for the performance of proton beam radiation therapy was revised collaboratively by the American College of Radiology (ACR) and the American Radium Society (ARS). This practice parameter was developed to serve as a tool in the appropriate application of proton therapy in the care of cancer patients or other patients with conditions in which radiation therapy is indicated. It addresses clinical implementation of proton radiation therapy, including personnel qualifications, quality assurance (QA) standards, indications, and suggested documentation., Materials and Methods: This practice parameter for the performance of proton beam radiation therapy was developed according to the process described under the heading The Process for Developing ACR Practice Parameters and Technical Standards on the ACR website (https://www.acr.org/Clinical-Resources/Practice-Parameters-and-Technical-Standards) by the Committee on Practice Parameters - Radiation Oncology of the ACR Commission on Radiation Oncology in collaboration with the ARS., Results: The qualifications and responsibilities of personnel, such as the proton center Chief Medical Officer or Medical Director, Radiation Oncologist, Radiation Physicist, Dosimetrist and Therapist, are outlined, including the necessity for continuing medical education. Proton therapy standard clinical indications and methodologies of treatment management are outlined by disease site and treatment group (e.g. pediatrics) including documentation and the process of proton therapy workflow and equipment specifications. Additionally, this proton therapy practice parameter updates policies and procedures related to a quality assurance and performance improvement program (QAPI), patient education, infection control, and safety., Conclusion: As proton therapy becomes more accessible to cancer patients, policies and procedures as outlined in this practice parameter will help ensure quality and safety programs are effectively implemented to optimize clinical care., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 Published by Elsevier B.V. on behalf of Particle Therapy Co-operative Group.)

Purpose: To report the current practice pattern of the proton stereotactic body radiation therapy (SBRT) for prostate treatments., Materials and Methods: A survey was designed to inquire about the practice of proton SBRT treatment for prostate cancer. The survey was distributed to all 30 proton therapy centers in the United States that participate in the National Clinical Trial Network in February, 2023. The survey focused on usage, patient selection criteria, prescriptions, target contours, dose constraints, treatment plan optimization and evaluation methods, patient-specific QA, and image-guided radiation therapy (IGRT) methods., Results: We received responses from 25 centers (83% participation). Only 8 respondent proton centers (32%) reported performing SBRT of the prostate. The remaining 17 centers cited 3 primary reasons for not offering this treatment: no clinical need, lack of volumetric imaging, and/or lack of clinical evidence. Only 1 center cited the reduction in overall reimbursement as a concern for not offering prostate SBRT. Several common practices among the 8 centers offering SBRT for the prostate were noted, such as using Hydrogel spacers, fiducial markers, and magnetic resonance imaging (MRI) for target delineation. Most proton centers (87.5%) utilized pencil beam scanning (PBS) delivery and completed Imaging and Radiation Oncology Core (IROC) phantom credentialing. Treatment planning typically used parallel opposed lateral beams, and consistent parameters for setup and range uncertainties were used for plan optimization and robustness evaluation. Measurements-based patient-specific QA, beam delivery every other day, fiducial contours for IGRT, and total doses of 35 to 40 GyRBE were consistent across all centers. However, there was no consensus on the risk levels for patient selection., Conclusion: Prostate SBRT is used in about 1/3 of proton centers in the US. There was a significant consistency in practices among proton centers treating with proton SBRT. It is possible that the adoption of proton SBRT may become more common if proton SBRT is more commonly offered in clinical trials., (© 2024 The Authors.)

Purpose: To report demographic and clinical characteristics of patients who were more likely to receive proton beam therapy (PBT) than photon therapy from facilities with access to proton centers., Materials and Methods: We utilized the national cancer database to identify the facilities with access to PBT between 2004 and 2015 and compared the relative usage of photons and PBT for demographic and clinical scenarios in breast, prostate, and nonsmall cell cancer., Results: In total, 231 facilities with access to proton centers accounted for 168 323 breast, 39 975 lung, and 77 297 prostate cancer patients treated definitively. Proton beam therapy was used in 0.5%, 1.5%, and 8.9% of breast, lung, and prostate cases. Proton beam therapy was correlated with a farther distance traveled and longer start time from diagnosis for each site ( P  < .05).For breast, demographic correlates of PBT were treatment in the west coast (odds ratio [OR] = 4.81), age <60 (OR = 1.25), white race (OR = 1.94), and metropolitan area (OR = 1.58). Left-sided cancers (OR = 1.28), N2 (OR = 1.71), non-ER+/PR+/Her2Neu- cancers (OR = 1.24), accelerated partial breast irradiation (OR = 1.98), and hypofractionation (OR = 2.35) were predictors of PBT.For nonsmall cell cancer, demographic correlates of PBT were treatment in the south (OR = 2.6), metropolitan area (OR = 1.72), and Medicare insurance (OR = 1.64). Higher comorbid score (OR = 1.36), later year treated (OR = 3.16), and hypofractionation (not SBRT) (OR = 3.7) were predictors of PBT.For prostate, correlates of PBT were treatment in the west coast (OR = 2.48), age <70 (OR = 1.19), white race (OR = 1.41), metropolitan area (OR = 1.25), higher income/education (OR = 1.25), and treatment at an academic center (OR = 33.94). Lower comorbidity score (OR = 1.42), later year treated (OR = 1.37), low-risk disease (OR = 1.45), definitive compared to postoperative (OR = 6.10), and conventional fractionation (OR = 1.64) were predictors of PBT., Conclusion: Even for facilities with established referrals to proton centers, PBT utilization was low; socioeconomic status was potentially a factor. Proton beam therapy was more often used with left-sided breast and low-risk prostate cancers, without a clear clinical pattern in lung cancer., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Background: Electromagnetic transponders bronchoscopically implanted near the tumor can be used to monitor deep inspiration breath hold (DIBH) for thoracic radiation therapy (RT). The feasibility and safety of this approach require further study., Methods: We enrolled patients with primary lung cancer or lung metastases. Three transponders were implanted near the tumor, followed by simulation with DIBH, free breathing, and 4D-CT as backup. The initial gating window for treatment was ±5 mm; in a second cohort, the window was incrementally reduced to determine the smallest feasible gating window. The primary endpoint was feasibility, defined as completion of RT using transponder-guided DIBH. Patients were followed for assessment of transponder- and RT-related toxicity., Results: We enrolled 48 patients (35 with primary lung cancer and 13 with lung metastases). The median distance of transponders to tumor was 1.6 cm (IQR 0.6-2.8 cm). RT delivery ranged from 3 to 35 fractions. Transponder-guided DIBH was feasible in all but two patients (96% feasible), where it failed because the distance between the transponders and the antenna was >19 cm. Among the remaining 46 patients, 6 were treated prone to keep the transponders within 19 cm of the antenna, and 40 were treated supine. The smallest feasible gating window was identified as ±3 mm. Thirty-nine (85%) patients completed one year of follow-up. Toxicities at least possibly related to transponders or the implantation procedure were grade 2 in six patients (six incidences, cough and hemoptysis), grade 3 in three patients (five incidences, cough, dyspnea, pneumonia, and supraventricular tachycardia), and grade 4 pneumonia in one patient (occurring a few days after implantation but recovered fully and completed RT). Toxicities at least possibly related to RT were grade 2 in 18 patients (41 incidences, most commonly cough, fatigue, and pneumonitis) and grade 3 in four patients (seven incidences, most commonly pneumonia), and no patients had grade 4 or higher toxicity., Conclusions: Bronchoscopically implanted electromagnetic transponder-guided DIBH lung RT is feasible and safe, allowing for precise tumor targeting and reduced normal tissue exposure. Transponder-antenna distance was the most common challenge due to a limited antenna range, which could sometimes be circumvented by prone positioning.

Radiation pneumonitis (RP) that develops early (i.e., within 3 mo) (RP Early ) after completion of concurrent chemoradiation (cCRT) leads to treatment discontinuation and poorer survival for patients with stage III non-small cell lung cancer. Since no RP Early risk model exists, we explored whether published RP models and pretreatment 18 F-FDG PET/CT-derived features predict RP Early Methods: One hundred sixty patients with stage III non-small cell lung cancer treated with cCRT and consolidative immunotherapy were analyzed for RP Early Three published RP models that included the mean lung dose (MLD) and patient characteristics were examined. Pretreatment 18 F-FDG PET/CT normal-lung SUV featured included the following: 10th percentile of SUV (SUV P10 ), 90th percentile of SUV (SUV P90 ), SUV max , SUV mean , minimum SUV, and SD. Associations between models/features and RP Early were assessed using area under the receiver-operating characteristic curve (AUC), P values, and the Hosmer-Lemeshow test (pHL). The cohort was randomly split, with similar RP Early rates, into a 70%/30% derivation/internal validation subset. Results: Twenty (13%) patients developed RP Early Predictors for RP Early were MLD alone (AUC, 0.72; P = 0.02; pHL, 0.87), SUV P10 , SUV P90, and SUV mean (AUC, 0.70-0.74; P = 0.003-0.006; pHL, 0.67-0.70). The combined MLD and SUV P90 model generalized in the validation subset and was deemed the final RP Early model (RP Early risk = 1/[1+e (- x ) ]; x = -6.08 + [0.17 × MLD] + [1.63 × SUV P90 ]). The final model refitted in the 160 patients indicated improvement over the published MLD-alone model (AUC, 0.77 vs. 0.72; P = 0.0001 vs. 0.02; pHL, 0.65 vs. 0.87). Conclusion: Patients at risk for RP Early can be detected with high certainty by combining the normal lung's MLD and pretreatment 18 F-FDG PET/CT SUV P90 This refined model can be used to identify patients at an elevated risk for premature immunotherapy discontinuation due to RP Early and could allow for interventions to improve treatment outcomes., (© 2024 by the Society of Nuclear Medicine and Molecular Imaging.)

Purpose: To assess radiation therapy (RT)-induced vasculitis in patients with non-small cell lung cancer (NSCLC) by examining changes in the uptake of 18 F-fluoro-D-deoxyglucose ([ 18 F]FDG) by positron emission tomography/computed tomography (PET/CT) images of the ascending aorta (AA), descending aorta (DA), and aortic arch (AoA) before and after proton and photon RT., Method: Thirty-five consecutive locally advanced NSCLC patients were definitively treated with proton (n = 27) or photon (n = 8) RT and concurrent chemotherapy. The patients were prospectively enrolled to undergo [ 18 F]FDG-PET/CT imaging before and 3 months after RT. An adaptive contrast-oriented thresholding algorithm was applied to generate mean standardized uptake values (SUVmean) for regions of interest (ROIs) 3 mm outside and 3 mm inside the outer perimeter of the AA, DA, and AoA. These ROIs were employed to exclusively select the aortic wall and remove the influence of blood pool activity. SUVmeans before and after RT were compared using two-tailed paired t-tests., Results: RT treatments were associated with increased SUVmeans in the AA, DA, and AoA-1.9%, 0.3%, and 1.3% for proton and 15.8%, 9.5%, and 15.5% for photon, respectively. There was a statistically significant difference in the ∆SUVmean (post-RT SUVmean - pre-RT SUVmean) in patients treated with photon RT when compared to ∆SUVmean in patients treated with proton RT in the AA (p = 0.043) and AoA (p = 0.015). There was an average increase in SUVmean that was related to dose for photon patients (across structures), but that was not seen for proton patients, although the increase was not statistically significant., Conclusion: Our results suggest that patients treated with photon RT for NSCLC may exhibit significantly more RT-induced inflammation (measured as ∆SUVmean) in the AA and AoA when compared to patients who received proton RT. Knowledge gained from further analyses in larger cohorts could aid in treatment planning and help prevent the significant morbidity and mortality associated with RT-induced vascular complications., Trial Registration: NCT02135679., (© 2023. The Author(s).)

Introduction: R0 resection and radiation therapy have been associated with improved overall survival (OS) in patients with thymic carcinoma (TC). Here, we analyzed which subgroups of patients derive the greatest benefit from postoperative radiation therapy (PORT)., Methods: Clinical, pathologic, treatment, and survival information of 462 patients with TC from the International Thymic Malignancy Interest Group/European Society of Thoracic Surgeons database were analyzed. Variables included age, sex, continent of treatment, paraneoplastic syndrome, carcinoma subtype, tumor size, pathologic Masaoka stage, resection status, and use of chemotherapy. OS was the primary end point using the Kaplan-Meier method. Time to recurrence (TTR) was the secondary end point using a competing risk analysis. A 3-month landmark analysis was performed., Results: PORT was associated with a significant OS benefit (5-y OS 68% versus 53%, p = 0.002). In patients with R0 resection, PORT was associated with increased OS for advanced (stages III-IV, p = 0.04), but not early (stages I-II, p = 0.14) stage TC. In patients with an R1/2 resection of advanced-stage TC, PORT was associated with significantly longer OS (5-y OS 53% versus 38%; p < 0.001). Subset analyses did not reveal clear associations of PORT with TTR. On multivariable analysis, lower pathologic stage, PORT, and R0 resection status were associated with an OS benefit, whereas only higher age and lower pathologic stage had an association with longer TTR., Conclusions: In the largest individual patient data set on patients with TC reported to date, PORT was associated with a meaningful OS benefit in patients with advanced-stage TC after an R0 or R1/2 resection., (Copyright © 2023 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.)

Introduction: Invisible ink tattoos (IITs) avoid cosmetic permanence of visible ink tattoos (VITs) while serving as more reliable landmarks for radiation setup than tattooless setups. This trial evaluated patient-reported preference and feasibility of IIT implementation., Methods and Materials: In an IRB-approved, single institution, prospective trial, patients receiving proton therapy underwent IIT-based treatment setup. A survey tool assessed patient preference on tattoos using a Likert scale. Matched patients treated using our institutional standard tattooless setup were identified; treatment times and image guidance requirements were evaluated between tattooless and IIT-based alignment approaches. Distribution differences were estimated using Wilcoxon rank-sum tests or Chi-square tests., Results: Of 94 eligible patients enrolled, median age was 58 years, and 58.5% were female. Most common treatment sites were breast (18.1%), lung (17.0%) and pelvic (14.9%). Patients preferred to receive IITs versus VITs (79.8% pre-treatment and 75.5% post-treatment, respectively). Patients were willing to travel farther from home to avoid VITs versus IITs (p<0.01). Females were willing to travel (45.5% vs. 23.1%; p=0.04) and pay additional money to avoid VITs (34.5% vs. 5.1%; p<0.01). Per-fraction average +treatment time and time from on table/in room to first beam were shorter with IIT-based vs. tattooless setup (12.3min vs. 14.1min; p=0.04 and 24.1min vs. 26.2min; p=0.02, respectively)., Discussion: In the largest prospective trial on IIT-based radiotherapy setup to date, we found that patients prefer IITs to VITs. Additionally, IIT-based alignment is an effective and efficient strategy in comparison with tattooless setup. Standard incorporation of IITs for patient setup should be strongly considered., Competing Interests: HL, CS, and JC report personal fees from Varian Medical Systems outside of the scope of this work. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Hardy-Abeloos, Gorovets, Lewis, Ji, Lozano, Tung, Yu, Hanlon, Lin, Kha, Yamada, Kabarriti, Lazarev, Hasan, Chhabra, Simone and Choi.)

Background: FLASH therapy is a treatment technique in which radiation is delivered at ultra-high dose rates (≥ 40 Gy/s). The first-in-human FAST-01 clinical trial demonstrated the clinical feasibility of proton FLASH in the treatment of extremity bone metastases. The objectives of this investigation are to assess the toxicities of treatment and pain relief in study participants with painful thoracic bone metastases treated with FLASH radiotherapy, as well as workflow metrics in a clinical setting., Methods: This single-arm clinical trial is being conducted under an FDA investigational device exemption (IDE) approved for 10 patients with 1-3 painful bone metastases in the thorax, excluding bone metastases in the spine. Treatment will be 8 Gy in a single fraction administered at ≥ 40 Gy/s on a FLASH-enabled proton therapy system delivering a single transmission proton beam. Primary study endpoints are efficacy (pain relief) and safety. Patient questionnaires evaluating pain flare at the treatment site will be completed for 10 consecutive days post-RT. Pain response and adverse events (AEs) will be evaluated on the day of treatment and on day 7, day 15, months 1, 2, 3, 6, 9, and 12, and every 6 months thereafter. The outcomes for clinical workflow feasibility are the occurrence of any device issues as well as time on the treatment table., Discussion: This prospective clinical trial will provide clinical data for evaluating the efficacy and safety of proton FLASH for palliation of bony metastases in the thorax. Positive findings will support the further exploration of FLASH radiation for other clinical indications including patient populations treated with curative intent., Registration: ClinicalTrials.gov NCT05524064., (© 2024. The Author(s).)

Bragg peak FLASH radiotherapy (RT) uses a distal tracking method to eliminate exit doses and can achieve superior OAR sparing. This study explores the application of this novel method in stereotactic body radiotherapy prostate FLASH-RT. An in-house platform was developed to enable intensity-modulated proton therapy (IMPT) planning using a single-energy Bragg peak distal tracking method. The patients involved in the study were previously treated with proton stereotactic body radiotherapy (SBRT) using the pencil beam scanning (PBS) technique to 40 Gy in five fractions. FLASH plans were optimized using a four-beam arrangement to generate a dose distribution similar to the conventional opposing beams. All of the beams had a small angle of two degrees from the lateral direction to increase the dosimetry quality. Dose metrics were compared between the conventional PBS and the Bragg peak FLASH plans. The dose rate histogram (DRVH) and FLASH metrics of 40 Gy/s coverage (V 40Gy/s ) were investigated for the Bragg peak plans. There was no significant difference between the clinical and Bragg peak plans in rectum, bladder, femur heads, large bowel, and penile bulb dose metrics, except for D max . For the CTV, the FLASH plans resulted in a higher D max than the clinical plans (116.9% vs. 103.3%). For the rectum, the V 40Gy/s reached 94% and 93% for 1 Gy dose thresholds in composite and single-field evaluations, respectively. Additionally, the FLASH ratio reached close to 100% after the application of the 5 Gy threshold in composite dose rate assessment. In conclusion, the Bragg peak distal tracking method can yield comparable plan quality in most OARs while preserving sufficient FLASH dose rate coverage, demonstrating that the ultra-high dose technique can be applied in prostate FLASH SBRT.

Purpose: Treatment options for recurrent esophageal cancer (EC) previously treated with radiation therapy (RT) are limited. Reirradiation (reRT) with proton beam therapy (PBT) can offer lower toxicities by limiting doses to surrounding tissues. In this study, we present the first multi-institutional series reporting on toxicities and outcomes after reRT for locoregionally recurrent EC with PBT., Methods and Materials: Analysis of the prospective, multicenter, Proton Collaborative Group registry of patients with recurrent EC who had previously received photon-based RT and underwent PBT reRT was performed. Patient/tumor characteristics, treatment details, outcomes, and toxicities were collected. Local control (LC), distant metastasis-free survival (DMFS), and overall survival (OS) were estimated using the Kaplan-Meier method. Event time was determined from reRT start., Results: Between 2012 and 2020, 31 patients received reRT via uniform scanning/passive scattering (61.3%) or pencil beam scanning (38.7%) PBT at 7 institutions. Median prior RT, PBT reRT, and cumulative doses were 50.4 Gy (range, 37.5-110.4), 48.6 Gy (relative biological effectiveness) (25.2-72.1), and 99.9 Gy (79.1-182.5), respectively. Of these patients, 12.9% had 2 prior RT courses, and 67.7% received PBT with concurrent chemotherapy. Median follow-up was 7.2 months (0.9-64.7). Post-PBT, there were 16.7% locoregional only, 11.1% distant only, and 16.7% locoregional and distant recurrences. Six-month LC, DMFS, and OS were 80.5%, 83.4%, and 69.1%, respectively. One-year LC, DMFS, and OS were 67.1%, 83.4%, and 27%, respectively. Acute grade ≥3 toxicities occurred in 23% of patients, with 1 acute grade 5 toxicity secondary to esophageal hemorrhage, unclear if related to reRT or disease progression. No grade ≥3 late toxicities were reported., Conclusions: In the largest report to date of PBT for reRT in patients with recurrent EC, we observed acceptable acute toxicities and encouraging rates of disease control. However, these findings are limited by the poor prognoses of these patients, who are at high risk of mortality. Further research is needed to better assess the long-term benefits and toxicities of PBT in this specific patient population., Competing Interests: J. Isabelle Choi and Charles B. Simone report personal fees from Varian Medical Systems outside of the scope of this work. Alexandra Hotca, Kunal K. Sindhu, Eric J. Lehrer, William F. Hartsell, Carlos Vargas, Henry K. Tsai, John H. Chang, Smith Apisarnthanarax, Romaine C. Nichols, Arpit M. Chhabra, Shaakir Hasan, Robert H. Press, Stanislav Lazarev, Carla Hajj, Rafi Kabarriti, and William G. Rule have no conflicts of interest to disclose., (© 2024 The Authors.)