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Men with Grade Group 2 (GG2) intermediate risk (IR) prostate cancer (PCa) have multiple curative radiation (RT) options. Compared to conventional external beam photon RT (XRT), including 3D-conformal RT (3DCRT) and IMRT, highly conformal RT techniques may provide less integral RT dose to normal tissue, including brachytherapy (BT), SBRT, and proton beam radiation therapy (PBT). These treatments require either advanced equipment and/or specialized training. Here we analyzed national trends in utilization of XRT, BT monotherapy, SBRT, and PBT, and assessed potential factors associated with receiving each technique. We hypothesize that socioeconomic and/or racial disparities are associated with differences in utilization of these specialized techniques. Men diagnosed with favorable IR PCa cancer, defined as Gleason 3+4 disease, PSA < 20 and clinical stage T1-T2 N0 M0, between 2004-2017 were identified in the National Cancer Database. Cohorts were defined as: XRT (3DCRT+IMRT, hypofractionated (HF) or standard fractionation (SF)), BT monotherapy (HDR, LDR), SBRT (5 fx) and PBT (HF or SF). Trends in utilization were examined. Associations between technique and patient, clinical disease, and sociodemographic characteristics were assessed by multivariable logistic regression, with P <0.05 considered significant. 71,140 patients met inclusion criteria of which 72.4% received standard XRT and 27.6 % received specialized radiation modalities (18.5% brachytherapy, 6.0% SBRT, & 3.1% PBT). Utilization of XRT and BT declined from 71.0% (XRT) and 27.5% (BT) in 2004 to 69.7% (XRT) and 17.2% (BT) in 2017. Receipt of SBRT and PBT increased from 0% (SBRT) and 1.45% (PBT) in 2004 to 9.9% (SBRT) and 3.3% (PBT) in 2017, respectively. On multivariable logistic regression, Black patients were less likely to receive BT (adjusted OR 0.79; 95%CI 0.74-0.83), SBRT (adjusted OR 0.77; 95%CI 0.70-0.85), or PBT (adjusted OR 0.39; 95%CI 0.33-0.47) compared to XRT (all P <0.0001). Socially disadvantaged seniors (SDS; age >65 years with Medicaid insurance) were less likely to receive specialized RT (adjusted OR 0.45; 95%CI 0.31-0.60; P<0.0001). Factors associated with increased likelihood of receiving BT, SBRT, or PBT included: treatment at Academic/Research center, treatment at a metropolitan facility, younger age, lower Charlson-Deyo Comorbidity Score, and lower PSA at presentation (all P < 0.01). Trends in utilization of RT modalities have dramatically changed in recent years with a sharp decline in BT, a doubling of PBT, and rapid adoption of SBRT, as coded in the NCDB. Compared to White patients with GG2 IR PCa, there are disparities in utilization of BT, SBRT, and PBT for Black patients and for SDS. It is unclear whether similar disparities exist for other prostate cancer grade groups for which BT and SBRT are being utilized. Future efforts should address access-to-care challenges for the use of these specialized techniques as they are expanded into higher GG. [ABSTRACT FROM AUTHOR]

Single-fraction high dose rate (HDR) prostate brachytherapy has shown improved actuarial biochemical control rates from 66% to 82% with dose escalation from 19 to 20.5 Gy, respectively, but is still inferior to the reported low dose rate brachytherapy control rates of over 90%. We aimed to identify whether dose escalation to 21, 23, and 25 Gy can be safely accomplished. Patients with previously untreated, pathologically confirmed, low-risk (cT1-T2a, Gleason ≤6, PSA <10 ng/mL) or favorable intermediate risk (Gleason 3+4, percentage of positive biopsy cores <50%, ≤1 NCCN intermediate risk factor) prostate adenocarcinoma were enrolled from a single institution. PSA and toxicity assessment were performed at baseline and at routine 6-month follow-ups. From May 9, 2018 to May 12, 2022, 18 patients were enrolled. None had received prior androgen deprivation therapy, 44% had low risk disease, and 61% were ECOG 0 at baseline. Median age was 68 years (total range: 43-79), and 83% were Caucasian. Eight patients received 21 Gy, nine patients received 23 Gy, and one patient received 25 Gy, with the 25 Gy cohort still accruing. The mean prostate size and range, determined by pre-operative prostate volume study on trans-rectal ultrasound, were as follows: 21Gy cohort (mean: 41.2cc; range: 21.9-63.1cc), 23Gy Cohort (mean: 41.2cc, range 28.3-71.7cc), 25Gy cohort (65.3cc). A median of 17 catheters (range: 16-20) were implanted. At a median follow-up of 35.7 months (range: IQR 4.4 - 50.2), only one grade 3 toxicity was reported, which was an ulcerative colitis (UC) flare noted in a patient whose UC was poorly controlled, requiring multiple courses of prednisone in the 6 months prior to his brachytherapy. Regarding toxicities attributable to therapy, fourteen and four patients experienced a grade 1 and 2 genitourinary toxicity respectively; four and four patients experienced a grade 1 and 2 reproductive system toxicity respectively; one patient experienced a grade 1 GI toxicity. Two patients needed foley catheters upon discharge, with neither requiring the foley long term. There were two treatment failures in the 21Gy cohort at 1.39 and 1.67 years from date of HDR brachytherapy; date of failure was defined by the first PSA 2.0ng/mL over nadir. Of these patients, one underwent focal salvage HDR, whilst the other underwent radical prostatectomy with only 1% of the volume involved by prostate cancer. Of note, there was seminal vesicle involvement on restaging prostate biopsy for the patient that underwent radical prostatectomy, however, this was not appreciated on the final prostatectomy specimen. Both patients have no evidence of disease currently. HDR brachytherapy appears well tolerated in patients with low to favorable intermediate risk prostate cancer at 21 and 23 Gy, with more accrual needed at 25Gy. Long-term follow-up needed to assess efficacy. [ABSTRACT FROM AUTHOR]

Organ preservation, an important goal in the treatment of head and neck squamous cell carcinoma (HNSCC), may include induction chemotherapy and cisplatin with radiation therapy (CRT). To our knowledge, no reports have directly compared the impact of induction chemotherapy with that of CRT on health-related quality of life (HRQOL). In a phase II trial, we assessed the HRQOL of patients treated with induction chemotherapy followed by CRT. Eligible patients had stage III–IV HNSCC. HRQOL questionnaires were administered at baseline, the end of induction (EOI), the end of CRT (EOCRT) and after CRT. Functional Assessment of Cancer Therapy (FACT version 4) assessed HRQOL. We carried out a comparison of changes in HRQOL from baseline to EOI and from EOI to EOCRT. This trial is registered with ClinicalTrials.gov (NCT01566435). Thirty patients were enrolled in the study. Most HRQOL questionnaires were completed (88%). The mean total FACT scores did not differ from baseline to EOI (general: 83.8 versus 79.1, P = 0.08; head and neck: 109.7 versus 105.8, P = 0.33; Total Outcome Index: 69.7 versus 62.3, P = 0.03; respectively, using P ≤ 0.01 to adjust for multiple simultaneous tests of differences). However, total FACT scores significantly worsened from EOI to EOCRT (79.1 versus 62.3, P = 0.01; 105.8 versus 74.2, P < 0.01; 62.3 versus 34.2, P = 0.01; respectively). Within domains, the head and neck cancer subscale score did not differ from baseline to EOI (median 28.5 versus 27.0, P = 0.69), but significantly worsened from EOI to EOCRT (27.0 versus 9.5, P < 0.01). Swallowing, oral pain and voice quality improved from baseline to EOI, but worsened from EOI to EOCRT. Physical and functional scores worsened from baseline to EOI and from EOI to EOCRT. The emotional well-being score improved from baseline to EOI but worsened from EOI to EOCRT. Overall, HRQOL did not significantly change from baseline to EOI but dramatically worsened from EOI to EOCRT. • Quality of life may be impaired by head and neck cancer and its treatment. • Organ preservation may include induction chemotherapy and cisplatin + radiation. • Overall, quality of life was not significantly impaired by induction chemotherapy. • Swallowing, oral pain and voice quality improved after induction therapy. • Overall, quality of life was dramatically worsened by cisplatin + radiation therapy. [ABSTRACT FROM AUTHOR]

Radiotherapy departments in low- and middle-income countries (LMICs) like Guatemala have recently introduced intensity-modulated radiotherapy (IMRT). IMRT has become the standard of care in high-income countries (HIC) due to reduced toxicity and improved outcomes in some cancers. The purpose of this work is to show the feasibility of adapting knowledge-based (KB) models established in a HIC to a LMIC lacking experience in IMRT to improve plan quality and planning efficiency. A Halcyon Linac was installed at our clinic in Guatemala in 2019 and has been used to treat approximately 90 patients daily with IMRT. A model developed on a cohort of head and neck cancer patients at a US academic radiotherapy center were applied at our center to create 20head and neck VMAT plans with different prescriptions, including simultaneous-integrated and sequential boosts. The plans created using the KB models achieved similar coverage of the planning target volume for each plan KB plans showed better 1) Parotid sparing with a mean dose reduction between 5%-25% and spinal cord maximum dose reduction between 3%-15%. The time efficiency to create VMAT plans using KB model versus manual planning improved four-fold, on average one hour versus more than 4 hours, respectively. Despite different prescriptions, guidelines and demographics of cancer patients between two institutions in a HIC and LMIC, this work demonstrates that KB planning can be used to generate better and more consistent VMAT plans versus manually created plans. In addition, KB planning has the potential to greatly increase planning efficiency higher efficiency and help address the shortage of medical physicists and dosimetrists in LMICs. [ABSTRACT FROM AUTHOR]

The utility of quality-of-life (QoL) measurements in daily clinical practice of cancer patients has been shown to influence decision making in 30.1% of medical interventions and in 63.2% of non-medical interventions. The purpose of our study was to assess the QoL of patients treated with radiotherapy at an upper middle-income country (UMIC). Fifty-five patients that were treated with 3D-conformal, Intensity-modulated radiation therapy, or Volumetric Modulated Arc Therapy techniques from September 2021 to December 2021(four months). QoL was assessed using (QLQ-C30) in Spanish with the permission from the European Organization for Research and Treatment of Cancer (EORTC). This was administered in-person before radiotherapy (RT) and six weeks after treatment via phone. A linear transformation to standardize the raw score was applied according to the EORTC QLC-30 Scoring Manual. Data analysis was performed using Stata 12 to compare the global health status, functional scale, symptom scale, mean scores and standard deviations with the EORTC Reference Values for cancer patients. Of the 55 patients treated with RT, 42 (76.4%) were female, 35 (63.6%) were ≥50 years old, with most being diagnosed with cervical (32.7%) and breast cancer (14.5%). Compared with the pre-RT scores at 6 weeks after RT completion, patients had a significant increase in their global health status from 62.2 to 71.78 compared to the baseline assessment (p value 0.06). Emotional functioning, fatigue, pain and insomnia showed no significant differences compared to before treatment. Further studies are needed in UMICs to understand how patient education and pretreatment information can help patients undergoing radiation therapy to cope with the process of therapy to better estimate predictors of quality of life after radiation therapy, and to see if patient reported QoL recovers over time at different timeline. [ABSTRACT FROM AUTHOR]

There is a vital need to train radiation oncology professionals in low-and middle-income countries (LMICs) to develop sustainable capacity and infrastructure for clinical oncology care. Radiotherapy departments in LMICs have started to introduce intensity-modulated radiotherapy (IMRT), which is widely utilized in high-income countries and has become the standard of care due to reduced toxicity and improved outcomes in a wide variety of cancers. This work reports on the initiatives and experience with the use of an online training and learning program for global radiation oncology education and training across three LMICs: Uganda, Mongolia and Guatemala Four interactive lectures and four sequential hands-on (step-by-step on IMRT processes) training sessions were given by radiation oncologists and medical physicists at XXX University in XXX, focusing on site-specific target definition, normal tissue contouring, IMRT planning and optimization, and IMRT QA. Additional four weeks of eight online videos and materials developed by XXX were provided to participants to review with quizzes after each week. Pre- and post- surveys, including 10-point confidence scores and free-response questions were performed to evaluate the outcome of the training sessions. Padlet was used as a platform for questions and answers during and after the training sessions. On average, 37 participants, including 15 radiation oncologists, 11 medical physicists, 5 dosimetrists, and 6 radiation therapists, participated in the virtual training sessions. Eighty percent of the participants responded to the surveys taken immediately following training. 66.7% had not received the IMRT training before. The level of confidence level using IMRT in the clinic increased from 3.25±1.98 to 5.25±2.20. Lessons learned include: 1. Hands-on training sessions are preferred to lectures; 2. Through virtual training, interactions between trainers and trainees are important to engage participants; 3. Different training sessions designed for specific groups (radiation oncologists, medical physicists, radiation therapists and dosimetrists) are needed to improve the relevance; 4. Online self-guided videos are easy to scale up but are a challenge to meet the specific needs of specific groups. 5. Language barrier is one of the limitations to performing the training for non-English speaking LMIC participants. Remote training provides an excellent and feasible e-learning platform to train radiotherapy professionals in LMICs. If adequately supported, the use of virtual training model can be an effective way to build capacity, as there are limited numbers of academically and clinically qualified radiation oncology professionals. These findings add to the limited knowledge of radiotherapy training developed for LMICs. [ABSTRACT FROM AUTHOR]

Radiotherapy departments in low- and middle-income countries (LMICs) have started introducing intensity-modulated radiotherapy (IMRT). IMRT has become the standard of care in high-income countries (HIC) due to reduced toxicity and improved outcomes in a wide variety of cancers. The purpose of this work is to demonstrate the feasibility of adapting knowledge-based planning (KBP) models established in a HIC to a LMIC lacking experience in IMRT to improve plan quality and planning efficiency. A new o-ring linear accelerator was installed at a hospital in Guatemala in 2019 and has been used to treat ∼80 patients daily with IMRT. Two KBP models developed on a cohort of prostate cancer patients at a university in the US were applied in the hospital in Guatemala to create 12 IMRT plans for 7 prostate patients with different prescriptions, including simultaneous-integrated and sequential boosts). Plan quality described by dose-volume histograms (DVH) metrics and planning time were compared between the plans created with the KBP models and those created manually by local dosimetrists or physicists. The plans created using these KBP models achieved similar or better coverage over the planning target volume in each plan, and showed a lower dose to bladder and rectum in 11 of 12 plans, and the remainder showed a comparable dose distribution and DVH for rectum and bladder. Sum plans showed better rectal sparing for all patients with V50Gy reduced between 1%-30.4% and bladder sparing for 6 of 7 patients with V50Gy reduced between 1.3% -16.8%. The time efficiency to create IMRT plans using KBP models improved three-fold, on average one hour versus three hours, respectively. Despite different prescriptions, guidelines and demographics of cancer patients between two institutions in a HIC and LMIC, this work demonstrates that KBP can be a useful tool in ensuring consistent, high-quality IMRT plans at institutions with little to no experience in inverse planning. In addition, KBP has the potential to improve capacity with higher efficiency and may help address the shortage of medical physicists and dosimetrists in LMICs. [ABSTRACT FROM AUTHOR]

Stereotactic body radiation therapy (SBRT) is an emerging treatment modality for clinically localized prostate cancer (PCa). Online daily adaptive radiotherapy (ART) could potentially improve the therapeutic ratio of prostate SBRT by accounting for inter-fraction variation in target and OAR volumes. To-date no group has evaluated the clinical utility of a novel AI-augmented CT-based ART system for prostate SBRT. In this study we hypothesized that adaptive prostate SBRT plans would result in improved target coverage and lower dose to OARs versus the unadapted treatment plan. Eight patients with unfavorable intermediate or high-risk PCa treated with 5-fx whole-pelvis prostate adaptive SBRT were reviewed. Patients were treated to the elective nodes (2500 cGy) with simultaneous boosts to the prostate/seminal vesicles (3625 cGy) and prostate (4000 cGy). 4 of 8 had rectal hydrogel spacer. For each Fx, CBCT was acquired and OARs (rectum, bladder, bowel, sigmoid, femurs) were segmented/deformed using AI. CTVs were rigidly registered. Volumes were adjusted manually and PTV expansions added. Adaptive treatment plans were developed based on the contoured targets and OARs and dose to these volumes for the adapted vs. initial plans were compared. The V100 (% PTV receiving prescription dose) and the D0.03 cc between scheduled and adapted treatment plans were compared using a Student's t-test, with significance threshold of P<0.05. Eight patients successfully completed 40 Fx's of adaptive RT as scheduled. Daily adaptation resulted in a statistically significant mean improvement in PTV V100 for all targets: [11.9% ± 2.1% for PTV 4000 (p <0.0001); 7.9% ± 1.5% for PTV 3625 (p <0.0001); and 6.1% ± 1.6% for PTV 2500 (p= 0.0007)]. Mean rectal D0.03 was significantly reduced by 45.4 cGy ± 10.8 cGy (p= 0.0002) per fraction (227 cGy/5 fractions) compared to the initial plans. There were no statistically significant differences between scheduled and adapted D0.03 to the bladder, sigmoid, or bowel (Table). No patients experienced acute CTCAE grade ≥3 GI/GU adverse events (median F/U 9.5 months). All statistically significant differences were maintained in the presence and absence of rectal hydrogel spacer. CT-based online adaptive SBRT resulted in statistically significant and clinically meaningful improvements in PTV coverage and D0.03cc dose to the rectum. A trial evaluating CT adaptive prostate SBRT is underway. [ABSTRACT FROM AUTHOR]

We assess the feasibility and dosimetric characteristics of CT-guided daily adaptive radiotherapy (CT-ART) for patients with muscle-invasive bladder cancer (MIBC). Compared to the scheduled treatment, we hypothesized that CT-ART would allow us to optimize target coverage and dose to organs at risk (OARs) by accounting for inter-fraction motion of the bladder and OARs. Four patients with cT2a-T4aN0M0 MIBC treated with hypofractionated RT or chemoRT at 2.75 Gy/Fx (55Gy/20) with empty bladder using CT-ART were retrospectively reviewed. There were 42 total fractions delivered with CT-ART. For each Fx, cone beam CT (CBCT) scans were acquired with artificial-intelligent segmented target and OARs. Contours were manually edited and a patient-specific internal target volume (ITV) was applied for bladder filling during the adaptive process. An adaptive plan (P A) was then created and optimized based on these volumes. Adaptive plan metrics for target/OARs were then compared to the initial plan (P I) for each Fx. The PTV_5500 V 100 (%), V 95 (%), D 97% (Gy), and D 95% (Gy); rectum D 47Gy (cc); and non-sigmoid bowel OARs were compared between the P I and P A plans using paired samples t-test (Table). CT-ART improved PTV coverage, with mean per Fx improvement of 12.4% and 28.3% for V 95 and V 100 and 0.4 Gy/Fx for both D 97% and D 95% (p <0.01 for all). The P I plan did not meet PTV V 100 ≥95% in 39 of 42 Fxs (92.9%) vs. 4 of 42 Fx (9.5%) with the P A plans. P A plans did not result in increased dose to OARs (Table). Median CT-ART treatment duration improved over time [median 33 min (range 30-47) for the last patient treated]. CT-based online adaptive radiation therapy was feasible and significantly improved PTV coverage without a corresponding increase in dose to OARs. This study demonstrates the potential value of CT-ART for MIBC. This approach will be tested in an upcoming phase II trial. [ABSTRACT FROM AUTHOR]

High-grade cT1 (HGT1) urothelial carcinoma of the bladder (UC) is an aggressive disease with a 4-year cancer-specific mortality of 36% in a large cystectomy series. NCCN guidelines recommend radical cystectomy as the preferred treatment for patients with (1) BCG-naive HGT1 with high-risk features or (2) for HGT1 disease that is BCG unresponsive or intolerant. Definitive concurrent chemoradiotherapy (CRT) has emerged as a promising bladder-sparing alternative treatment for HGT1 with the recent presentation of the single-arm RTOG 0926 trial. However, while there is level 1 evidence that CRT is superior to radiotherapy (RT) alone for muscle-invasive bladder cancer (MIBC), there is limited data on the comparative effectiveness of RT vs. CRT for HGT1 non-MIBC. We hypothesized that CRT would be associated with improved overall survival (OS) vs. RT for patients with HGT1 bladder cancer. Patients with cT1N0M0, high-grade urothelial carcinoma diagnosed between 2004-2017 and treated with transurethral resection of the bladder tumor followed by RT alone or concurrent CRT were identified in the National Cancer Database (NCDB). All patient received a cumulative RT dose ≥ 50 Gy. Patients with a Charlson-Deyo comorbidity index (CDCI) score > 1 or missing key information were excluded. Propensity-weighted multivariable analysis (MVA) using Cox regression modeling was used to compare overall survival (OS) between groups. Covariables included age, race, ethnicity, gender, year of diagnosis, CDCI score, insurance status, educational and socioeconomic metrics, and treatment at an academic center. A total of 192 patients with HGT1 UC were treated with: (i) RT alone (n = 78) or (ii) CRT (n = 114). Median age was 81 (range: 50-90), and 70% were male. The median tumor size was 4.0 cm (range: 0.4-10.5 cm). The median follow-up time was 46 months (range: 10-168 months). The mean radiation dose was 62.4 Gy (SD: ±5 Gy) and 63.2 Gy (SD: ±12 Gy) in the RT and CRT cohorts, respectively. Propensity-weighted MVA showed that combined modality treatment with CRT was associated with improved OS relative to radiation alone [Hazard Ratio (HR): 0.56, 95% Confidence Interval (95% CI): 0.36-0.89, p = 0.012]. Female gender was associated with worse OS (HR: 1.75, 95% CI 1.16-2.66, p =.008). 4-year OS for the RT alone versus CRT arm was 22% and 38%, respectively. For patients with HGT1 bladder cancer, concurrent CRT was associated with improved OS compared with radiation alone. These results complement the findings of RTOG 0926 showing the promise of CRT for the treatment of HGT1 disease and support the decision by NRG Oncology investigators to omit RT alone as a treatment arm in the successor trial to RTOG 0926 for HGT1 disease. [ABSTRACT FROM AUTHOR]

Purpose/objective(s): A novel iodinated rectal hydrogel spacer (I-RS) has been developed to make the gel radiopaque on CT compared to the standard rectal hydrogel spacers (S-RS). As the iodine in I-RS strongly absorbs kV photons, the accuracy of currently employed CT calibration built into a single energy CT (SECT) becomes inaccurate to determine the proton stopping power ratio (PSR) of the injected gel. Direct measurements of PSR mediated by I-RS with proton beams has been reported; however, those measurements were conducted under ideal conditions without fully accounting for density heterogeneity mediated by air bubbles co-injected with the gel during placement. This study used dual-energy CT (DECT) to estimate I-RS PSR in patients undergoing CT simulation for prostate cancer (PCa) radiotherapy (RT).Materials/methods: Sequential scans at 90 and 140 kVp were acquired for 7 intact PCa (I-RS n = 5, S-RS n = 2) on a Philips Brilliance scanner. PSR was reconstructed following the method proposed by Torikoshi and improved by Yang, and compared to similar measurements when I-RS was replaced with S-RS. A pre-calculated table correlating effective atomic number with all possible Hounsfield Unit (HU) combinations from two sequential scans was implemented to accelerate reconstruction. PSRs were compared between DECT and SECT, and between I-RS and S-RS.Results: In gel, HU measurements were heterogeneous (range -372 - +358). The mean PSR on reconstruction when using DECT was 0.966 (0.940-0.980) for I-RS. Replacement of I-RS with S-RS HU density resulted in a mean PSR of 0.937 (0.926-0.941) by DECT. PSR for I-RS on SECT was 1.107, and 1.014 for S-RS. The estimated difference between PSR in I-RS and S-RS on DECT vs. SECT were 14% and 8%, respectively.Conclusion: These data demonstrate that the use of I-RS in proton RT treatment planning could overestimate proton range due to underestimating PSR when CT simulation is performed using standard SECT. Notably, PSR absolute value reported here is different compared to previously reported in vitro data under ideal conditions and may be related to differences in gel heterogeneity in vivo. Heterogeneity is highlighted by the wide range of gel HU measurements. Direct measurements of PSR will be obtained in a planned future experiment. These data suggest that PSR overestimation due to I-RS should be considered when planning PCa treatment using proton therapy for patients who get I-RS to reduce treatment toxicity. [ABSTRACT FROM AUTHOR]

The primary hypothesis of this multi-arm, non-randomized, phase 2 trial was that weight loss, a quantifiable surrogate of mucositis, would be less during de -escalated postoperative adjuvant cisplatin plus radiation therapy (de -POACRT: cisplatin 100 mg/m2 x1 dose; RT 42 Gy given in standard fractionation of 200 cGy/day) compared to historical POACRT (cisplatin 100 mg/m2 x3 doses; RT 60-66Gy) in patients with human papillomavirus-positive oropharynx squamous-cell carcinoma (HPV+ OPSCC). Patients with operable AJCC 8th Edition clinical stage I-III (excluding T 1-2 N 0 , T 4 , and N 3) HPV+ OPSCC underwent surgery. Risk-directed adjuvant therapy included: de -POACRT for high-risk pathology (positive margin, extra-nodal extension), de –POART (42 Gy) for intermediate-risk pathology (lympho-vascular or peri-neural invasion, ≥2 involved regional lymph nodes, lymph node >3 cm, and T 3 or N 2 pathology), and POACRT for T 4 or N 3 pathology. The primary endpoint was percent weight change from the first to the last day of de -POACRT. We hypothesized a 50% reduction in mean percent weight change (H 1 -3.7% for de -POACRT vs H 0 -7.4% [SD=5.46] for historical POACRT). Assuming a cohort distribution of 3:5:1, a sample of 60 patients would accrue 20 patients to de -POACRT, resulting in a power of 0.80 to detect H 1 using a two-sided test with α 0.05. The generalized estimating equation model with identity link function was used to calculate percent weight change. Key secondary acute toxicity endpoints included mean percent weight change during de -POART and POACRT, and change in serum creatinine and requirement for narcotics in each arm. Efficacy endpoints included relapse and death. We enrolled and treated 54 patients with adjuvant therapy: de -POACRT-20, de -POART-30, and POACRT-4. Mean percent weight change during de -POACRT was -4.89 (SEM 0.69; 95%CI -6.24, -3.54), which is significantly different from historical POACRT (p=0.0003). Mean percent weight change during de -POART was -3.18 (SEM 0.52; 95%CI -4.19, -2.17), and during POACRT was -10.11 (SEM 2.89; 95%CI -15.79, -4.43). In each arm, no significant change in serum creatinine from baseline to six weeks after adjuvant therapy occurred. The proportion of patients taking narcotics six weeks after adjuvant therapy was 40% for de -POACRT, 20% for de -POART, and 75% for POACRT. Median follow-up of all patients was 21.0 months (range 7.4- 32.6). Relapse occurred in 1 patient in each of the de -POACRT and de -POART cohorts and in three patients in the POACRT cohort. Death occurred in no patients in the de -POACRT and de -POART cohorts and in one patient in the POACRT cohort. Among patients with HPV+ OPSCC, the mean percent weight loss during de -POACRT was significantly less than during historical POACRT. [ABSTRACT FROM AUTHOR]

Purpose/objective(s): Polyethylene glycol (PEG) hydrogel perirectal spacers can reduce prostate cancer (PCa) radiotherapy (RT)-related gastrointestinal (GI) toxicity. Accurate hydrogel contouring requires T2 MRI simulation (sim), as hydrogels have Hounsfield units (HU) comparable to soft tissue on computerized tomography (CT). A PEG hydrogel containing covalently bound iodine was recently developed and approved for clinical use. However, its characteristics in routine clinical practice have yet to be reported. Here we evaluated iodinated hydrogel volume, perirectal spacing, and HU from treatment images for PCa patients receiving RT at our institution.Materials/methods: Patients with biopsy-proven, clinically localized PCa (cT1c-cT2N0M0) who had same-day CT/MRI sim after fiducial markers and iodinated hydrogel placement were identified. Hydrogel was contoured on CT sim, MRI, and cone beam CT (CBCT) at treatment start (CBCT#1) and completion (CBCT#2). Prostate and hydrogel volumes and anterior-posterior mid-gland perirectal spacing at midline were measured on CT/MRI and CBCTs, and HU was measured on CT sim and CBCTs using treatment planning software. Patient differences were evaluated using paired, two-tailed Student's t-tests, with significance at P < 0.05.Results: Twenty-three patients were identified (mean age 71.1 ± 7.8 years; mean prostate volume 61.9 ± 29.2 cm3; mean initial PSA 7.36 ± 1.9), treated with IMRT: 79.2 Gy/44 fx (n = 3), 70 Gy/28 fx (n = 15), or 36.25 Gy/5 fx (n = 5). Hydrogel was identified on all sim scans and was larger on T2 MRI vs CT (MRI mean volume 9.9 ± 1.7 cm3 vs CT 9.3 ± 1.6 cm3 vs; P = 0.03), and comparable mean perirectal distance at mid-gland/midline (MRI 1.02 ± 0.55 cm vs CT 1.03 ± 0.53 cm; P = 0.65). Perirectal spacing was maintained between CT sim and CBCT#1 (1.03 ± 0.51 cm; P = 0.97) done an average of 16.7 ± 7.1 days post sim and CT sim and CBCT#2 (1.03 ± 0.53 cm vs 1.02 ± 0.54; P = 0.74) done an average of 53.8 ± 19 days post sim. No significant change in hydrogel volume between CBCT#1 and CBCT#2 for 44 fx (10.9 ± 1.7 cm vs 10.4 ± 1.3 cm; P = 0.17), 28 fx (10.2 ± 1.4 vs 9.83 ± 1.7 cm; P = 0.11), or 5 fx (9.9 ± 2.1 vs 9.54 ± 1.9; P = 0.45) patients was observed. Hydrogel mean HU on CT sim was not significantly changed at CBCT#1 (CT sim 152.1 ± 30.5 vs CBCT#1 129.1 ± 51.6; P = 0.08), but mean HU at CBCT#2 (109.3 ± 47.9 cm) was lower vs CT sim (P = 0.001). For 44 fx treatments hydrogel HU significantly decreased between CBCT#1 and CBCT#2 (140.7 ± 10.0 vs 94.2 ± 80.4; P = 0.01), but not for 28 fx (123.5 ± 54.4 vs 103.4 ± 44.0; P = 0.13) or 5 fx (138.4 ± 38.5 vs 136 ± 37.2; P = 0.60) regimens.Conclusion: PEG-based iodinated hydrogel can be delineated on CT sim comparable to MRI sim, and maintains visibility and perirectal spacing through 5, 28, and 44 fx RT courses as assessed by CBCT. Hydrogel HU decreased over 44 fx relative to CT sim, with no significant difference in HU seen for 28 fx and 5 fx courses. Use of perirectal hydrogel containing covalently bound iodine may obviate reliance on T2 MRI for accurate hydrogel contouring during RT treatment planning. [ABSTRACT FROM AUTHOR]