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Radiation therapy is often used to treat meningioma with adverse features or when unresectable. Proton therapy has advantages over photon therapy in reducing integral dose to the brain. This study compared the incidence of radiological and clinical adverse events after photon versus proton therapy in the treatment of meningioma. A retrospective review was conducted on patients with meningioma treated with proton or photon therapy at two high-volume tertiary cancer centers. Patients with a history of prior radiation therapy (RT) or less than 3 months of follow-up were excluded. Post-RT imaging changes were categorized into abnormal T2 signal intensities (T2 changes) or abnormal T1 post-contrast and T2 signal intensities (T1c+T2 changes) on magnetic resonance imaging (MRI). Clinical outcomes of adverse events and survival were compared between the proton and photon therapies. Among the total of 77 patients, 38 patients received proton therapy and 39 patients received photon therapy. The median age at diagnosis was 55 years and median follow-up was 2.2 years. No significant differences in symptomatic adverse events were observed between the two groups: grade ≥ 2 adverse events were seen in 4 (10.5%) patients in the proton group and 3 (7.7%) patients in the photon group (p = 0.67). The 2-year cumulative incidences of T2 changes were 38.3% after proton therapy and 47.7% after photon therapy (p = 0.53) and the 2-year cumulative incidences of T1c+T2 changes were 26.8% after proton therapy and 5.3% after photon therapy (p = 0.02). One patient experienced grade ≥ 4 adverse event in each group (p = 0.99). Estimated 2-year progression-free survival was 79.5% (proton therapy 76.0% vs. photon therapy 81.3%, p = 0.66) and 2-year overall survival was 89.7% (proton therapy 86.6% vs. photon therapy 89.3%, p = 0.65). Following RT, high rates of T2 changes were seen in meningioma patients regardless of treatment modality. Proton therapy was associated with significantly higher rates of T1c+T2 changes compared with photon therapy, but severe adverse events were uncommon in both groups and survival outcomes were comparable between the two groups. Future studies will aim at correlating the MRI changes with models that can be incorporated into RT planning to avoid toxicity.

Purpose Criteria by the Radiologic Assessment in Neuro-Oncology (RANO) group outline the diagnosis of pseudoprogression (Ps) after photon therapy for gliomas based on timing and location. We noted that patients receiving proton therapy manifested radiographic changes that appear different than Ps after photon therapy, which could be interpreted as tumor progression. In this study, we retrospectively reviewed MR imaging after proton or photon radiation for gliomas. We propose criteria to characterize proton pseudoprogression (ProPs) as distinct from Ps seen after photons. Methods Post-treatment MR imaging, clinical and pathological data of low grade glioma patients were reviewed. Overall, 57 patients receiving protons were reviewed for the presence of ProPs, and 43 patients receiving photons were reviewed for any equivalent imaging changes. Data collected included the location and timing of the new enhancement, tumor grade, molecular subtype, chemotherapy received, and clinical symptoms. Results Fourteen patients (24.6%) had new enhancement following radiation therapy that was unique to treatment with protons. The mean time to development of the ProPs was 15.4 months (7–27 months). We established the following criteria to characterize ProPs: located at the distal end of the proton beam; resolves without tumor-directed therapy; and subjectively multifocal, patchy, and small (

The purpose of our study is to assess the impact of COVID-19 on the clinical responsibilities, training, and wellness of US radiation oncology residents. An anonymous cross-sectional survey was sent to all 91 radiation oncology residency programs in the USA. The survey included questions related to demographics, changes in clinical duties and training, job prospects, and wellness indicators. Univariate and multivariate logistic regression analyses were used to evaluate factors associated with residents endorsing high satisfaction with their departments’ response to COVID-19. A total of 96 residents completed the survey from 67 US radiation oncology programs. In the multivariate logistic regression model, remote contouring (OR: 3.91 (95% CI: 1.11, 13.80), p = 0.03) and belief that one will be adequately trained to independently practice after completing residency (OR: 4.68 (1.12, 19.47), p = 0.03) were significantly associated with high resident satisfaction with their department’s response to COVID-19. Most residents indicated that hypofractionation was encouraged to a greater extent (n = 79, 82.3%), patients were triaged by disease risk (n = 67, 69.8%), and most agreed/strongly agreed that they have been provided with adequate personal protective equipment (PPE) (n = 85, 88.5%). The COVID-19 pandemic has affected the training and wellness of radiation oncology residents. Our analysis suggests that radiation oncology programs might increase resident satisfaction with their department’s response to COVID-19 by enabling remote contouring and working with residents to identity and remedy possible concerns regarding their ability to independently practice post residency. Supplementary Information The online version contains supplementary material available at 10.1007/s13187-021-01993-5.

Purpose Brachytherapy is an irreplaceable component of gynecologic cancer treatment. Resident training has declined, and procedural exposure is variable. We evaluated whether simulation-based gynecologic brachytherapy training among radiation oncology residents could improve knowledge, confidence, and interest. Methods and Materials Before a brachytherapy workshop, radiation oncology residents without prior gynecologic brachytherapy experience completed a survey on brachytherapy knowledge, procedural confidence, plan evaluation, and quality/safety. Residents then participated in a gynecologic brachytherapy workshop. Lectures covered brachytherapy imaging and physics principles/quality assurance, followed by hands-on and individualized feedback regarding applicator selection and placement, target segmentation, and physics quality assurance. Afterward, preworkshop questions were recollected. Descriptive statistics and Fisher's exact tests were used for data analysis. Results After the workshop, resident responses regarding the learning environment and baseline knowledge questions improved overall. There was a 30% improvement in favorable responses to the learning environment statement “My residency has a formal process/curriculum to teach brachytherapy” and for baseline knowledge the greatest improvement was seen for “I am familiar with the anatomy and placement of the applicators in relation to the anatomy”. “Lack of didactic or procedural training exposure” was identified as the main reason for declining brachytherapy use. Initially, 1/8 residents correctly completed the knowledge questions, and after the workshop, 6/7 (p Conclusions Domain-specific knowledge, procedural confidence, and brachytherapy interest improved after a gynecologic brachytherapy workshop. Integrated didactic and simulation-based brachytherapy training may serve as a valuable learning tool to augment resident knowledge, introduce practical skills, and spark resident interest in brachytherapy.

Background The American Radium Society (ARS) Appropriate Use Criteria brain malignancies panel systematically reviewed (PRISMA [Preferred Reporting Items for Systematic Reviews and Meta-Analyses]) published literature on neurocognitive outcomes after stereotactic radiosurgery (SRS) for patients with multiple brain metastases (BM) to generate consensus guidelines. Methods The panel developed 4 key questions (KQs) to guide systematic review. From 11 614 original articles, 12 were selected. The panel developed model cases addressing KQs and potentially controversial scenarios not addressed in the systematic review (which might inform future ARS projects). Based upon quality of evidence, the panel confidentially voted on treatment options using a 9-point scale of appropriateness. Results The panel agreed that SRS alone is usually appropriate for those with good performance status and 2–10 asymptomatic BM, and usually not appropriate for >20 BM. For 11–15 and 16–20 BM there was (between 2 case variants) agreement that SRS alone may be appropriate or disagreement on the appropriateness of SRS alone. There was no scenario (among 6 case variants) in which conventional whole-brain radiotherapy (WBRT) was considered usually appropriate by most panelists. There were several areas of disagreement, including: hippocampal sparing WBRT for 2–4 asymptomatic BM; WBRT for resected BM amenable to SRS; fractionated versus single-fraction SRS for resected BM, larger targets, and/or brainstem metastases; optimal treatment (WBRT, hippocampal sparing WBRT, SRS alone to all or select lesions) for patients with progressive extracranial disease, poor performance status, and no systemic options. Conclusions For patients with 2–10 BM, SRS alone is an appropriate treatment option for well-selected patients with good performance status. Future study is needed for those scenarios in which there was disagreement among panelists.

Purpose: As a means of limiting normal tissue toxicity, proton-beam therapy (PBT) is an emerging radiation modality for glioblastoma (GBM) reirradiation. However, data for recurrent GBM treated with PBT reirradiation is limited. Therefore, we analyzed treatment patterns, toxicities, and clinical outcomes of patients with recurrent GBM treated with PBT reirradiation using the multi-institutional Proton Collaborative Group registry. Methods and Materials: Prospectively collected data for patients with recurrent GBM who underwent PBT while enrolled in Proton Collaborative Group study 01-009 (NCT01255748) were analyzed. We evaluated overall survival (OS), progression-free survival (PFS), and toxicity. Toxicities were scored per the Common Terminology Criteria for Adverse Events, version 4.0. Descriptive statistics were used to report patient, tumor, and treatment characteristics. Multivariable analyses (MVA) for toxicity were conducted using logistic regression. The Kaplan-Meier method was used to calculate OS and PFS. MVA for OS and PFS was conducted using Cox proportional-hazards models. The SAS statistical software was used for the analysis. Results: We identified 45 recurrent patients with GBM who underwent PBT reirradiation between 2012 and 2018. The median time between initial GBM diagnosis and recurrence was 20.2 months. The median follow-up time from PBT reirradiation was 10.7 months. Median PFS was 13.9 months (95% confidence interval [CI], 8.23-20.0 months) and median OS was 14.2 months (95% CI, 9.6-16.9 months) after PBT reirradiation. One patient experienced an acute grade 3 toxicity, 4 patients experienced late grade 3 toxicity (no grade ≥4 toxicities). MVA revealed that prior surgery was associated with a 91.3% decreased hazard of death (hazard ratio: 0.087; 95% CI, 0.02-0.42; P < .01). No explanatory variables were associated with PFS or grade 3 toxicities. Conclusions: This is the largest series to date reporting outcomes for PBT reirradiation of patients with recurrent GBM. Our analysis indicates that PBT is well tolerated and offers efficacy rates comparable with previously reported photon reirradiation.

OBJECTIVES We studied a cohort of cancer patients that underwent curative-intent radiation within the last year of life (LYOL). Given the unexpectedly short survival, we evaluated the proportion with relapsed/refractory disease, determined causes of death, and explored whether treatment intent was associated with aggressiveness of care at the end of life. MATERIALS AND METHODS We extracted and linked claims data and radiotherapy records for patients seen at a single academic institution that died between October 1, 2014, and September 30, 2015. RESULTS Among 870 cancer patients, 290 were irradiated within the LYOL, of which 287 had treatment intent recorded (101 curative-intent, 186 palliative-intent). The majority of curative-intent patients had hematologic malignancies and/or underwent transplant (44.6%), followed by head and neck (9.9%) and gastrointestinal malignancies (9.9%). Half (n=49; 48.5%) had relapsed/refractory disease at the time of curative-intent radiation, including 13 with metastatic disease. Tumor progression (n=65; 64.4%) was the most common cause of death, followed by treatment-related mortality (n=27; 26.7%), of which transplant/hematologic malignancy patients (n=19) were the majority. Compared with palliative-intent patients, curative-intent patients had significantly higher rates of chemotherapy use within 14 days of death (P=0.04), intensive care unit stay within 30 days of death (P

Radiation therapy (RT) is a mainstay in the interdisciplinary treatment of brain tumors of the skull base and brain. Technical innovations during the past 2 decades have allowed for increasingly precise treatment with better sparing of adjacent healthy tissues to prevent treatment-related side effects that influence patients' quality of life. Particle therapy with protons and charged ions offer favorable kinetics with sharp dose deposition in a well-defined depth (Bragg-Peak) and a steep radiation fall-off beyond that maximum. This review highlights the role of particle therapy in the management of primary brain tumors and tumors of the skull base.

Treatment of ocular tumors on dedicated scattering-based proton therapy systems is standard afforded due to sharp lateral and distal penumbras. However, most newer proton therapy centers provide pencil beam scanning treatments. In this paper, we present a pencil beam scanning (PBS)-based ocular treatment solution. The design, commissioning, and validation of an applicator mount for a conventional PBS snout to allow for ocular treatments are given. In contrast to scattering techniques, PBS-based ocular therapy allows for inverse planning, providing planners with additional flexibility to shape the radiation field, potentially sparing healthy tissues. PBS enables the use of commercial Monte Carlo algorithms resulting in accurate dose calculations in the presence of heterogeneities and fiducials. The validation consisted of small field dosimetry measurements of point doses, depth doses, and lateral profiles relevant to ocular therapy. A comparison of beam properties achieved through the applicator against published literature is presented. We successfully showed the feasibility of PBS-based ocular treatments.

Purpose: The optimal salvage treatment for malignant glioma after prior radiotherapy (RT) is not well established. Proton therapy (PT) is an attractive treatment modality for reirradiation (ReRT) of recurrent disease; however, data are limited.Methods: The prospective, multi-institutional Proton Collaborative Group (PCG) registry was queried for patients with malignant glioma who previously received RT and underwent PT-ReRT between 7/2011-10/2018. Overall survival (OS) and progression-free survival (PFS) were assessed using the Kaplan-Meier method and Cox proportional hazards regression analysis. Results: 109 consecutive patients were identified. Median follow-up was 11.2 months and median time interval (TI) from prior RT (median 59.3 Gy) to PT-ReRT (median 49.6 Gy) was 45.7 months. Primary histology was glioblastoma (n=62), oligodendroglioma (n=26), and astrocytoma (n=20). Median PFS and OS was 6.1 and 11.1 months, respectively. On UVA, improved PFS was associated with oligodendroglioma (HR 0.39) and astrocytoma (HR 0.55) histologies, WHO Grade III (HR 0.36), TI (HR 0.989), surgical resection (HR 0.39), and PT-ReRT dose ≥50 Gy (HR 0.59) (all p

Purpose Racial and ethnic minorities in the state of Washington experience higher cancer mortality relative to whites. We sought to characterize differences in travel distance to radiation therapy (RT) facilities in Washington by race and ethnicity with a special focus on non-Hispanic American Indians and Alaska Natives as a contributor to limited access and cancer disparities. Methods and Materials Geocoded mortality data from Washington Department of Health (2011-2018) were used to identify decedents with mortality related to all-causes, all cancers, and cancers likely requiring access to RT. This was determined from optimal RT usage estimates by diagnosis. RT facility locations were ascertained from the Directory of Radiation Therapy Centers and confirmed. Distance from decedents’ address listed on death certificates to nearest RT facility was calculated. Generalized mixed models were used for statistical analysis. Results We identified 418,754 deaths; 109,134 were cancer-related, 60,973 likely required RT. Among decedents with cancers likely requiring RT, non-Hispanic American Indians and Alaska Natives decedents would have had to travel 1.16 times (95% confidence interval [CI], 1.09-1.24) farther from their residences to reach the nearest treatment facility compared with non-Hispanic whites. This association existed in metro counties but was more pronounced in nonmetro counties (1.39 times farther; 95% CI, 1.22-1.58). In addition, Hispanics would have had to travel 1.11 times farther (95% CI, 1.06-1.16) to reach the nearest facility compared with non-Hispanic whites, primarily due to differences in urban counties. Decedents in nonmetro counties lived on average 35 miles (SD = 29) from RT centers and non-Hispanic American Indians and Alaska Natives in nonmetro counties 53 miles (SD = 38). Compared with non-Hispanic white decedents, those who were non-Hispanic black, non-Hispanic Asian, and non-Hispanic Native Hawaiian decedents lived closer to RT facilities. Conclusions We observed significant disparities in access to RT facilities in Washington, specifically for non-Hispanic American Indians and Alaska Natives and rural decedents. The findings call for initiatives to improve access to critical cancer treatment services for these underserved populations with known disparities in cancer deaths.

Germ cell tumors are rare CNS tumors predominantly diagnosed in pediatric and young adult patients. They are divided into two broad groups, germinoma and non-germinomatous germ cell tumor, based on management strategies. Radiotherapy is an integral part of the management of CNS germ cell tumors. Judicious target delineation and selection of radiation dose are crucial to a favorable therapeutic ratio.

Late and long-term sequelae of treatment for patients with brain tumors can greatly affect their quality of life, daily functioning, and even mortality. Though some late effects are permanent, many can be mitigated or addressed with interventions. Thus, it is important to follow patients long term to monitor for treatable late effects and recognize other unexpected toxicities from radiation therapy. This chapter outlines possible late effects and treatments after brain irradiation.

Whole brain radiation therapy has been a mainstay of treatment for patients with brain metastases for many years. The role of whole brain radiation therapy has changed with the introduction of stereotactic radiosurgery and systemic therapies with CNS penetration, but remains and important option for patients with multiple metastases and/or leptomeningeal disease. With the advent of IMRT, techniques such as hippocampal avoidance have become possible. This chapter outlines the basic approach to techniques in delivering whole brain radiation therapy for brain metastases.

The classification of lower-grade gliomas has been greatly altered since the 2016 World Health Organization (WHO) introduced molecular diagnostics as part of their recommendations. Clinical trials that dictate treatment approaches, however, are based on histological classification. This chapter addresses the standard guidelines for contouring and planning for treatment of lower-grade gliomas, as well as clinical pearls for imaging.

PURPOSE Radiologic Assessment in Neuro-Oncology (RANO) criteria define pseudoprogression (Ps) after photon radiation for gliomas, as occurring less than twelve weeks from radiation, within the high dose radiation field. However, some patients receiving proton manifest lesions that appear subjectively different from photon Ps based on timing and location (more than six months from radiation and deeper to the prior tumor), which would be called tumor progression by RANO. We retrospectively reviewed MRI changes after proton or photon radiation for gliomas. We propose criteria to characterize proton pseudoprogression (ProPs) distinct from photon pseudoprogression or tumor progression. METHODS Post-treatment MRIs of patients with gliomas were reviewed, along with clinical and pathological data. 77 proton patients were reviewed for the presence of ProPs, and 64 photon patients were reviewed for imaging changes. Data collected included the location, timing, and morphology of the lesions, tumor type, chemotherapy, and clinical symptoms. RESULTS 16 (21%) of the patients who received protons had imaging changes unique to protons, at a mean of 14.6 months after radiation. We established the following criteria to characterize ProPs: not immediately in or adjacent to the resection cavity; ~ 2cm opposite from target beam entry; can resolve without treatment; subjectively multifocal, patchy, small (< 1cm). None of the photon patients had lesions that met our criteria for ProPs (p< 0.001). CONCLUSION Patients who receive protons can have a unique subtype of pseudoprogression (Ps), which we refer to as proton pseudoprogression (or ProPs). These lesions could be mistaken for tumor progression, but typically resolve spontaneously. ProPs can possibly be explained by the increased relative biological effectiveness of protons and beam angle selection which may deposit at ~2cm deep to the target. Recognizing these lesions can prevent unnecessary treatment for mistaken tumor progression, especially in the context of clinical trials that include proton.

IMPORTANCE: Although stereotactic radiosurgery (SRS) is preferred for limited brain metastases from most histologies, whole-brain radiotherapy (WBRT) has remained the standard of care for patients with small cell lung cancer. Data on SRS are limited. OBJECTIVE: To characterize and compare first-line SRS outcomes (without prior WBRT or prophylactic cranial irradiation) with those of first-line WBRT. DESIGN, SETTING, AND PARTICIPANTS: FIRE-SCLC (First-line Radiosurgery for Small-Cell Lung Cancer) was a multicenter cohort study that analyzed SRS outcomes from 28 centers and a single-arm trial and compared these data with outcomes from a first-line WBRT cohort. Data were collected from October 26, 2017, to August 15, 2019, and analyzed from August 16, 2019, to November 6, 2019. INTERVENTIONS: SRS and WBRT for small cell lung cancer brain metastases. MAIN OUTCOMES AND MEASURES: Overall survival, time to central nervous system progression (TTCP), and central nervous system (CNS) progression-free survival (PFS) after SRS were evaluated and compared with WBRT outcomes, with adjustment for performance status, number of brain metastases, synchronicity, age, sex, and treatment year in multivariable and propensity score–matched analyses. RESULTS: In total, 710 patients (median [interquartile range] age, 68.5 [62-74] years; 531 men [74.8%]) who received SRS between 1994 and 2018 were analyzed. The median overall survival was 8.5 months, the median TTCP was 8.1 months, and the median CNS PFS was 5.0 months. When stratified by the number of brain metastases treated, the median overall survival was 11.0 months (95% CI, 8.9-13.4) for 1 lesion, 8.7 months (95% CI, 7.7-10.4) for 2 to 4 lesions, 8.0 months (95% CI, 6.4-9.6) for 5 to 10 lesions, and 5.5 months (95% CI, 4.3-7.6) for 11 or more lesions. Competing risk estimates were 7.0% (95% CI, 4.9%-9.2%) for local failures at 12 months and 41.6% (95% CI, 37.6%-45.7%) for distant CNS failures at 12 months. Leptomeningeal progression (46 of 425 patients [10.8%] with available data) and neurological mortality (80 of 647 patients [12.4%] with available data) were uncommon. On propensity score–matched analyses comparing SRS with WBRT, WBRT was associated with improved TTCP (hazard ratio, 0.38; 95% CI, 0.26-0.55; P

Purpose To characterize the participation of radiation oncology (RO) in reporting quality metrics through the Centers for Medicare and Medicaid Services’ (CMS) Hospital Compare database and to describe the association of hospital characteristics with RO-specific quality metrics. Methods and Materials Data from the CMS Hospital Compare, International Atomic Energy Agency’s Directory of Radiotherapy Centre, 2010 US Census, and CMS Inpatient Prospective Payment System were linked to create an integrated data set of geographic information, facility characteristics, and quality measures, focusing on the use of external beam radiation therapy (EBRT) for bony metastases. Results Of 4829 hospitals in the Hospital Compare database, 2030 had access to radiation therapy. Among these, 814 (40%) reported on the rate of guideline-concordant EBRT for bony metastases, a RO-specific quality measure. A total of 33,614 eligible cases of bony metastases treated with EBRT were sampled. Participation in quality reporting varied significantly by geography, population type, teaching status, hospital ownership, hospital type, and hospital size. The median rate of guideline-concordant palliative EBRT utilization was 89%. Nine percent of 814 centers had a compliance rate of less than 50%. On multivariable analysis, increasing number of cases sampled (odds ratio 0.93, P = .028), increasing hospital star-rating, and above-average patient experience rating (odds ratio 0.58, P = .024) remained significantly associated with decreased odds of falling into the lowest quartile of guideline-concordant EBRT utilization. Conclusions RO participation in a large, national quality improvement effort is nascent and reveals potential quality gaps between hospitals offering palliative EBRT for bone metastases. More robust RO-specific quality measures are needed.

Background Stereotactic radiosurgery (SRS) is a treatment modality that is frequently used as salvage therapy for small nodular recurrent high-grade gliomas (HGG). Due to the infiltrative nature of HGG, it is unclear if this highly focused technique provides a durable local control benefit. Objective To determine how demographic or clinical factors influence the pattern of failure following SRS for recurrent high-grade gliomas. Methods We retrospectively reviewed clinical, radiographic, and follow-up information for 47 consecutive patients receiving SRS for recurrent HGG at our institution between June 2006 and July 2016. All patients initially presented with an HGG (WHO grade III and IV). Following SRS for recurrence, all patients experienced treatment failure, and we evaluated patterns of local, regional, and distant failure in relation to the SRS 50% isodose line. Results Most patients with recurrent HGG developed "in-field" treatment failure following SRS (n = 40; 85%). Higher SRS doses were associated with longer time to failure (hazards ratio = 0.80 per 1 Gy increase; 95% confidence interval 0.67-0.96; P = .016). There was a statistically significant increase in distant versus in-field failure among older patients (P = .035). This effect was independent of bevacizumab use (odds ratio = 0.54, P = 1.0). Conclusion Based on our experience, the majority of treatment failures after SRS for recurrent HGG were "in-field." Older patients, however, presented with more distant failures. Our results indicate that higher SRS doses delivered to a larger area as fractioned or unfractioned regimen may prolong time to failure, especially in the older population.

BACKGROUND The American Society for Radiation Oncology (ASTRO) issued a Choosing Wisely recommendation (CWr) against use of intensity modulated radiotherapy (IMRT) as part of breast conservation therapy in 2013, noting that “its routine use has not been demonstrated to provide significant clinical advantage”. Also, as IMRT is more expensive vs conventional radiotherapy (cRT), use in this setting may represent wasteful spending. The aims of this study were to characterize: 1) IMRT use immediately preceding the ASTRO CWr, 2) the cost-consequences of IMRT vs. cRT in the year after breast cancer diagnosis, and 3) excess annual U.S. national expenditure on IMRT in this setting. METHODS Surveillance Epidemiology and End Results (SEER) records for women age ≥66 years with a first primary diagnosis of Stage I/II breast cancer (2007-2012) were linked with Medicare claims (2007-2013). All cases had coverage for ≥12-months before/after diagnosis (or until death), and to be consistent with the CWr, had lumpectomy 1 month before to 6 months after diagnosis, and radiation therapy within 6 months of lumpectomy. We evaluated receipt of IMRT vs cRT within 1 year of diagnosis in 12 SEER registries. We also calculated mean direct medical expenditure in the year after diagnosis by summing all allowable charges from Medicare claims. Costs were inflated to 2017 USD. We evaluated differences in means by registry using ANOVA and compared mean costs for cases treated with IMRT vs cRT using t-test. We projected excess annual U.S. national expenditure on IMRT (vs. cRT) using the findings from aims 1 & 2 and assuming 209000 incident Stage I/II cases and that 55% receive lumpectomy. RESULTS Among 13037 women meeting all inclusion criteria, mean age was 74, 89.0% were white, and 19.8% received IMRT. Table 1 shows the proportions receiving IMRT by SEER registry and mean cost for cases treated with IMRT vs cRT. The proportion with IMRT varied significantly between registries (p Table 1: Results for Selected RegistriesRegistry% with IMRTMean Cost in Year After Dx ($) IMRTcRTpAll 12 Registries19.84314533501 DISCUSSION From 2007-2013, use of IMRT in Stage I/II breast cancer was substantial (19.8%) and varied significantly across SEER registries. Cases treated with IMRT incurred significantly higher cost ($9644) in the year following diagnosis vs. those treated with cRT. If patterns of care remain similar today, there is potentially as much as $219 million in annual U.S. national expenditure on low-value radiotherapy following lumpectomy. Our findings suggest an opportunity to improve quality in cancer care while reducing expenditure by curbing use of IMRT. Future studies should develop interventions to align practice with ASTRO CW recommendations and reduce variation in practice between regions. Citation Format: Roth JA, McDougall J, Halasz L, Fedorenko C, Sun Q, Patel S. IMRT use after lumpectomy in early-Stage breast cancer: Patterns of care and cost-consequences [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-11-14.

Purpose/Objective(s) Racial and ethnic minorities in Washington State (WA) experience higher cancer mortality relative to whites. We sought to characterize differences in travel distance as a marker for access to radiation therapy (RT) facilities in WA and one possible contributing factor to cancer disparities. Materials/Methods Geocoded mortality data from the WA Department of Health (2011-2018) were used to identify decedents with mortality related to all causes, all cancers, and cancers likely requiring access to RT (defined as estimated RT usage rate > 50% by anatomical subsite corresponding to ICD-9 or 10 code). Race was defined per US Office of Management and Budget 1997 standard and ethnicity as Hispanic or non-Hispanic. RT facility locations were identified from the Directory of Radiotherapy Centers and validated by internet search or phone calls. Road network distance from decedent's residence to nearest RT facility was calculated on a geographic information platform. Generalized mixed models were used for statistical analysis. Results We identified 109,134 cancer-related deaths of which 60,973 likely required RT. Among decedents with cancers likely requiring RT, non-Hispanic (NH) American Indian/Alaskan Native (AI/AN) decedents would have had to travel 1.16 times (95% CI 1.09-1.24) farther to reach the nearest treatment facility compared to NH whites. This association existed in metro counties but was more pronounced in non-metro and rural counties, where NH AI/ANs would have had to travel 1.39 times farther compared to NH whites (95% CI 1.22 – 1.58). This translated to an average of 83 miles (SD = 22) for NH AI/AN in rural areas to travel to RT centers whereas NH Whites in rural areas would have had to travel on average 59 miles (SD = 28). Hispanics would have had to travel 1.11 times farther to reach the nearest facility compared to NH whites (95% CI 1.06 – 1.16), primarily due to differences in urban areas. NH African American, NH Asian, and NH Native Hawaiian decedents lived closer to RT facilities compared to the NH white decedents. Based on our findings, we estimated that expanding the federal “safe harbor” restrictions on health systems providing transportation from 50 to 75 miles could open up needed services for 96% of rural NH AI/ANs. Conclusion NH AI/ANs and rural decedents experience stark disparities in access to RT facilities in WA state. The findings call for creative initiatives to improve access to critical cancer treatment services to combat racial, ethnic and rural disparities in cancer deaths. In depth analysis of local barriers to access for minority communities is necessary to devising practical solutions such as advocating for policy change for “safe harbor” restrictions.

PURPOSE/OBJECTIVE(S) To investigate radiation oncology (RO) program directors' (PDs) attitudes and practices regarding racial and ethnic diversity, equity and inclusion (DEI) and to better understand their potential impact on underrepresented in medicine (UIM) residents in RO. MATERIALS/METHODS A 28-item IRB-approved survey was developed using the validated Ethnic Harassment Experiences Scale and the Daily Life Experiences subscale, as well as input from DEI leaders in RO. Apart from demographics, questions were either True/False or graded on a Likert scale. The Likert-scaled questions are reported as agreement (strongly agree and agree) or disagreement (strongly disagree or disagree). The survey was administered using an online survey platform to PDs from the 90 ACGME-accredited programs. Descriptive statistics were used for data analysis. RESULTS The response rate was 71% (64/90). Demographics: 59% were male and 41% female. 66% were White, 25% Asian, < 2% Black and < 2% Hispanic. Institutional Culture and Beliefs: Most (75%, N = 48) reported at least one UIM faculty and 52% had a UIM faculty in a leadership role. 42% responded that they had a department DEI director. A minority (17%, N = 11) agreed "I believe that people from UIM backgrounds have equal access to quality tertiary education.... in the US." The majority (97%, N = 62) agreed "My program values residents from UIM backgrounds." Support and Resources: Majority (78%, N = 50) agreed "My program has resources in place to assist/provide support for resident physicians from UIM backgrounds," and a minority (19%, N = 12) agreed "My program has supported a UIM resident to apply for an NIH Diversity Supplement award." Interview and Recruitment: Most PDs (53%) had not taken part in activities aimed at recruiting UIM residents and 17% had interviewed no UIM applicants in the past 5 years for residency. In response to "How many total UIM students has your department matriculated?" 19% (N = 12) did not provide an answer, 20% (N = 13) answered unsure/did not know and 6% (N = 4) had matriculated zero UIM applicants. Resident experiences of Racism: 17% (N = 11) agreed "UIM residents in my program have reported incidents of racism to me," and 28% (N = 18) agreed "I believe that UIM residents in my program have been treated differently because of their race/ethnicity by faculty, staff, co-residents or patients." CONCLUSION Our survey results show that most (75%) RO PDs believe that UIM persons do not have equal access to tertiary education in the US (17% disagreed and 8% were neutral), but that UIM residents are supported in their department (78%). Most PDs reported that they do not participate in specific activities aimed at recruiting UIM residents, with nearly 1 in 5 programs reporting no interviews of UIM applicants in the last 5 years, and over one quarter of programs acknowledging differential treatment based on race/ethnicity. These data suggest a potential disconnect between DEI perceptions and activities among RO PDs that may be addressed through increased awareness and tailored programs.

Multisession stereotactic radiation therapy is increasingly being seen as a preferred option for intracranial diseases in close proximity to critical structures and for larger target volumes. The objective of this study is to investigate the reproducibility of the Extend system from Elekta. A retrospective review was conducted for all patients treated with multisession Gamma Knife between July 2010 and June 2015, including both malignant and benign lesions. Eighty-four patients were treated in this 5-year span. The average residual daily setup uncertainty was 0.48 (0.19) mm. We compare measurements of setup uncertainty from the Extend system to measurements performed with a linac-based approach previously used in our center. The Extend system has significantly reduced setup uncertainty for fractionated intracranial treatments at our institution. Positive results were observed in a small population of edentulous patients. The Extend system compares favorably with other approaches to delivering intracranial stereotactic radiotherapy and is a robust, simple-to-use, and precise method for treating multisession intracranial lesions.

Purpose: Improved mammographic and surgical techniques and pathologic evaluation, particularly greater attention to achieving negative margins, have resulted in decreased local recurrence rates for patients with ductal carcinoma in situ (DCIS). This is an updated analysis of local outcomes after breast-conserving surgery (BCS) and adjuvant radiation therapy (RT) at a single institution in the modern era. Methods and Materials: We retrospectively reviewed the records of 245 women treated for DCIS with BCS and RT between 2001 and 2007. Competing risk analysis was used to calculate local recurrence (LR) as a first event with the development of a second non-breast malignancy, contralateral breast cancer, and death as competing first events. The median age at diagnosis was 54 (range, 32-84) and 174 (93%) women had estrogen receptor (ER) and/or progesterone receptor (PR) positive disease. Ninety-five (39%) were grade III. Specimen radiograph during surgery was obtained for 223 women (91%) and post-operative mammogram for 102 (42%). Half underwent more than one excision. The institutional goal for margins during the study period was 3 mm or greater; final margins were >2 mm in 221 (90%). All received adjuvant radiation therapy to the whole breast (median whole breast dose: 4400; range, 4000 - 5220) and nearly all (99%) received a boost to the surgical cavity (median boost dose: 1600; range, 800 – 1800). Among patients with ER and/or PR+ disease, 105 (60%) received adjuvant hormonal therapy. Results: At a median follow-up of 10.6 years, 4 patients had a LR (2 DCIS, 2 invasive ductal carcinoma) as a first event with a cumulative LR incidence of 0.0% and 1.5% at 5 and 10 years, respectively. The 5 and 10-year cumulative incidence of the competing first events is seen in the table below. Twenty women developed a contralateral breast cancer (CBC; 8 DCIS, 12 invasive carcinoma), 13 were diagnosed with a second non-breast malignancy (3 endometrial, 2 fallopian tube, 1 gallbladder, 1 leukemia and thyroid, 4 lung, 1 ovarian, and 1 uterine), and 7 died. Family history, age at diagnosis, and receipt of hormonal therapy were not significantly associated with the development of CBC on univariable analysis (all p>0.05). Incidence of local recurrence and competing eventsEvent5-year cumulative incidence10-year cumulative incidenceLocal recurrence0.0%1.5%Contralateral Breast Cancer2.5%7.9%Second non-breast malignancy2.6%4.5%Death1.2%3.5% Conclusions: With longer follow-up, our rates of local recurrence following breast-conserving therapy for DCIS remain very low (1.5% at 10 years). The vast majority of patients had >2 mm margins, specimen radiographs, and received a tumor bed boost. The majority (60%) of patients with hormone receptor positive disease received adjuvant endocrine therapy. The 10-year incidence of CBC was higher than expected. Predisposing factors for the development of CBC are worthy of investigation. Citation Format: Warren LE, Chen Y-H, Halasz LM, Capuco A, Bellon JR, Brock JE, Punglia RS, Wong JS, Harris JR. Improved long-term outcomes of breast-conserving therapy for women with ductal carcinoma in situ [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-17-07.

Purpose In 2013, the American Society for Radiation Oncology (ASTRO) issued a Choosing Wisely recommendation against the routine use of intensity modulated radiotherapy (IMRT) for whole breast irradiation. We evaluated IMRT use and subsequent impact on Medicare expenditure in the period immediately preceding this recommendation to provide a baseline measure of IMRT use and associated cost consequences. Methods and materials SEER records for women ≥66 years with first primary diagnosis of Stage I/II breast cancer (2008–2011) were linked with Medicare claims (2007–2012). Eligibility criteria included lumpectomy within 6 months of diagnosis and radiotherapy within 6 months of lumpectomy. We evaluated IMRT versus conventional radiotherapy (cRT) use overall and by SEER registry (12 sites). We used generalized estimating equations logit models to explore adjusted odds ratios (OR) for associations between clinical, sociodemographic, and health services characteristics and IMRT use. Mean costs were calculated from Medicare allowable costs in the year after diagnosis. Results Among 13,037 women, mean age was 74.4, 50.5% had left-sided breast cancer, and 19.8% received IMRT. IMRT use varied from 0% to 52% across SEER registries. In multivariable analysis, left-sided breast cancer (OR 1.75), living in a big metropolitan area (OR 2.39), living in a census tract with ≤$90,000 median income (OR 1.75), neutral or favorable local coverage determination (OR 3.86, 1.72, respectively), and free-standing treatment facility (OR 3.49) were associated with receipt of IMRT (p

Improved imaging, surgical techniques, and pathologic evaluation likely have decreased local recurrence rates for patients with ductal carcinoma in situ (DCIS). We present long-term outcomes of a large single-institution series after breast-conserving surgery (BCS) and adjuvant radiation therapy (RT). We retrospectively reviewed the records of 245 women treated for DCIS with BCS and RT between 2001 and 2007. Competing risk analysis was used to calculate local recurrence (LR) as a first event with the development of a second non-breast malignancy, contralateral breast cancer, and death as competing first events. At a median follow-up of 10.6 years, 4 patients had a LR (2 DCIS, 2 invasive) as a first event with a cumulative LR incidence of 0.0% and 1.5% at 5 and 10 years, respectively. Most patients had > 2 mm margins (90%), specimen radiographs (93%), and received a tumor bed boost (99%). The majority (60%) of patients with hormone receptor-positive disease received adjuvant endocrine therapy. Ten-year cumulative incidence of contralateral breast cancer (CBC) was 7.9%, second non-breast malignancy was 4.5%, and death unrelated to breast cancer was 3.5%. Family history, age at diagnosis, and receipt of endocrine therapy were not significantly associated with the development of CBC (all P > 0.05). With mature follow-up, our rates of local recurrence following breast-conserving therapy for DCIS remain very low (1.5% at 10 years). The incidence of CBC was higher than the LR incidence. Predisposing factors for the development of CBC are worthy of investigation.

BACKGROUND The optimal treatment for patients with brain metastases remains controversial as the use of stereotactic radiosurgery (SRS) alone, replacing whole-brain radiation therapy (WBRT), has increased. This study determined the patterns of care at multiple institutions before 2010 and examined whether or not survival was different between patients treated with SRS and patients treated with WBRT. METHODS This study examined the overall survival of patients treated with radiation therapy for brain metastases from non–small cell lung cancer (NSCLC; initially diagnosed in 2007-2009) or breast cancer (initially diagnosed in 1997-2009) at 5 centers. Propensity score analyses were performed to adjust for confounding factors such as the number of metastases, the extent of extracranial metastases, and the treatment center. RESULTS Overall, 27.8% of 400 NSCLC patients and 13.4% of 387 breast cancer patients underwent SRS alone for the treatment of brain metastases. Few patients with more than 3 brain metastases or lesions ≥ 4 cm in size underwent SRS. Patients with fewer than 4 brain metastases less than 4 cm in size (n = 189 for NSCLC and n = 117 for breast cancer) who were treated with SRS had longer survival (adjusted hazard ratio [HR] for NSCLC, 0.58; 95% confidence Interval [CI], 0.38-0.87; P = .01; adjusted HR for breast cancer, 0.54; 95% CI, 0.33-0.91; P = .02) than those treated with WBRT. CONCLUSIONS Patients treated for fewer than 4 brain metastases from NSCLC or breast cancer with SRS alone had longer survival than those treated with WBRT in this multi-institutional, retrospective study, even after adjustments for the propensity to undergo SRS. Cancer 2016;122:2091–100. © 2016 American Cancer Society.

BACKGROUND LC is a late and often fatal manifestation of advanced EGFR mutated NSCLC with up to 9% of patients developing LC. Given the higher incidence of LC in EGFR mutated tumors, we hypothesized it may have unique imaging and clinical characteristics. METHODS We identified 23 patients with EGFR mutated NSCLC and LC treated at a large academic institution between 2016 and 2019. Clinical and treatment characteristics were obtained from the electronic medical record. Radiographic subtype of LC and presence of ventriculomegaly were determined by independent review of available brain and spine MRI imaging. RESULTS Among 23 eligible patients, mean age was 57 years, 96% had advanced NSCLC at diagnosis and 61% had EGFR exon 19 deletion. Median time from NSCLC diagnosis to LC development was 23 months (95% CI:13–33), with only 17% of patients presenting with LC in the absence of parenchymal brain metastases. Of the 91% of patients with radiographic evidence of LC, equal numbers had nodular or linear LC (22% each) and 39% had a mixed presentation. Additionally, 30% of patients had evidence of spinal LC. Ventriculomegaly was present in 52% of patients, with 48% developing clinical symptoms of hydrocephalus and 13% receiving shunt placement. Median overall survival (OS) from time of LC diagnosis was 3.9 months (95% CI:2.7–10.0), which is lower than in prior published studies. Patients with nodular LC and absence of ventriculomegaly fared better with a median OS of 6.5 months and 5.7 months respectively. CONCLUSIONS OS is poor in patients with LC associated with EGFR mutated NSCLC, although appears better in patients with nodular LC. The high incidence of hydrocephalus emphasizes the need for its early recognition and treatment. Further studies are needed to identify promising treatment strategies and to determine factors associated with improved OS in this population.

e14540 Background: Glioblastoma (GBM) is the most common primary central nervous system (CNS) malignancy. In recent years, molecular and histological analyses have identified GBM with primitive neuronal component (GBM-PNC) as a distinct entity with poor regional control and worse overall prognosis. GBM-PNCs are more prone to CNS dissemination and leptomeningeal (LM) metastasis, occurring in up to 40% of patients. Given the concern for distal CNS spread, we hypothesized that craniospinal irradiation (CSI) may be an effective treatment option for GBM-PNC. Methods: We performed a retrospective chart review of patients diagnosed with GBM-PNC treated at a large academic center with institutional review board approval. Clinical, histologic and treatment characteristics, as well as disease outcomes were obtained from the electronic medical record. Results: Ten patients diagnosed with GBM-PNC were identified in the period of 2005-2019. Median follow-up was 17 months. Overall, 80% of patients were men, median age was 49 years (range 20-64) and ECOG 0-1. Fifty percent of patients received CSI as opposed to involved field radiation therapy (IFRT). Four of five patients receiving CSI were treated with proton therapy. All patients, but one received concurrent Temozolomide. Both IFRT and CSI were tolerated well with minimal grade 3-4 toxicities. Patients treated with CSI were more likely to experience transient grade 3-4 lymphopenia (60% vs 0%). Eighty percent of patients experienced a recurrence after treatment with median progression free survival (PFS) of 13 months (range 8-26). PFS did not differ between patients receiving IFRT and CSI (14 vs 12.5 months, p = 0.9). Median overall survival (OS) was 30 months for patients who received IFRT, and median OS was not reached in the CSI group. Of the patients who received CSI as part of their treatment, all recurrences were within the high dose radiation area. On the contrary, 75% of patients who received IFRT experienced multiple recurrences at new intracranial sites and later in the leptomeninges or the spine, requiring multiple treatment courses. Conclusions: This hypothesis generating study demonstrates that CSI may prevent distant intracranial metastasis and LM disease progression. CSI delivered with proton therapy was well tolerated with minimal additional toxicity. A larger study is needed to guide the optimal treatment of patients diagnosed with glioblastoma with primitive neuronal component.

With maximal safe surgical resection, radiation therapy, and chemotherapy, many patients with oligodendroglioma live for several years after diagnosis. Many of these survivors suffer long-term sequelae of radiation therapy, including neurocognitive decline, endocrine dysfunction, and secondary malignancy. Several clinicians and investigators have thus sought to eliminate or delay radiation therapy for these patients. Proton therapy utilizes the unique properties of the Bragg peak to decrease the overall integral dose to the brain and adjacent organs. Dosimetric studies and single arm trials suggest promising toxicity outcomes for proton therapy compared to photon therapy, however comparative trials are lacking. Overall, especially with continued technological advances to further the precision and understanding of dose delivery, proton therapy represents a promising way to decrease the late effects of radiation therapy for patients with oligodendroglioma.

PURPOSE This study examines the relationship between dose to corneal substructures and incidence of corneal toxicity within 6 months of proton beam therapy (PBT) for uveal melanoma. We aim to develop clinically meaningful dose constraints that can be used to mitigate corneal toxicity. METHODS AND MATERIALS Ninety-two patients were treated with PBT between 2015 and 2017 and evaluated for grade 2+ (GR2+) intervention-requiring corneal toxicity in our prospectively maintained database. Most patients were treated with 50 Gy (relative biological effectiveness [RBE]) in 5 fractions, and all had complete six-month follow-up. Analyses included Mann-Whitney, χ2, Fisher exact, and receiver operating curve tests to identify risk factors for GR2+ toxicity. Bivariate logistic regression was used to identify independent dose-volume histogram (DVH) predictors of toxicity after adjustment for the most important clinical risk factor. RESULTS The 6-month PBT GR2+ corneal toxicity rate was 10.9%, with half of patients experiencing grade 2 toxicity and half experiencing grade 3 toxicity, with no grade 4 events. Patients with anterior chamber tumors had a higher risk (58.3%) for toxicity than those with posterior tumors (0%) or posterior tumors extending past the equator (25%, P

Although conventional photons and protons are roughly equivalent biologically, proton therapy has a superior dose distribution given that the majority of dose is deposited as a localized peak (Bragg peak) without exit radiation dose. By minimizing dose to nearby organ structures, proton therapy for primary brain and spine tumors may (1) reduce acute and late toxicity (neurocognition, endocrine dysfunction, secondary malignancies) and/or (2) allow dose escalation to improve local control. The reduction in morbidity with proton therapy is best exemplified in treatment of medulloblastoma, which involves irradiation of the craniospinal axis and posterior fossa. By sparing anterior midline structures of the chest, abdomen, pelvis, in addition to cochlea and pituitary, evidence suggests lower rates of acute toxicity, endocrinopathy, and lower predicted rates of secondary malignancies. Proton therapy has been associated with excellent local control rates for primary bone tumors (chondrosarcoma, chordoma) at the base of skull and spine, especially in the adjuvant setting. Prospective and multi-institutional retrospective studies suggest excellent outcomes with protons for other primary brain and spine tumors, including low grade gliomas, ependymoma, craniopharyngioma, meningiomas, and pituitary adenomas.

Spine tumor is a broad term including primary and metastatic tumors. Only a minority of spine tumors are primary tumors. They include the vertebral column (bone) tumors, intradural-extramedullary tumors, and intramedullary tumors.

Optic nerve sheath meningiomas (ONSM) are rare, and usually benign, tumors involving meninges surrounding the optic pathway. They have a higher incidence in middle-aged females. Diagnosis is heavily reliant on magnetic resonance imaging (MRI). ONSM can be subclassified as primary ONSM (pONSM) and secondary ONSM (sONSM). ONSM, in general, exhibit slowly progressive enlargement, which invariably leads to visual symptoms and/or vision loss. Although surgery may have a role in sONSM, it commonly leads to postoperative blindness with pONSM. Radiotherapy (RT) remains the mainstay of treatment for this condition. Highly conformal RT techniques such as stereotactic fractionated RT (SFRT) have been shown to be effective in retaining functional vision, with low treatment-related morbidity. At fractionated doses of 50–54 Gy, almost all patients achieve local control, and 80% or more of patients report vision improvement or stabilization. In this chapter, we will review the clinical findings and the treatment recommendations for this condition.

This report describes a solitary orbital metastasis of lobular carcinoma in a woman 35 years after diagnosis of right breast lobular carcinoma in situ (LCIS). After partial response to anastrozole, the patient was treated with proton radiotherapy to 45 cobalt gray equivalents (CGE) with an excellent response. We additionally discuss treatment strategies for this rare metastatic site.

Importance The use of a radiotherapy (RT) boost to the tumor bed after whole-breast RT (WBRT) for ductal carcinoma in situ (DCIS) is largely extrapolated from invasive cancer data, but robust evidence specific to DCIS is lacking. Objective To compare ipsilateral breast tumor recurrence (IBTR) in women with DCIS treated with vs without the RT boost after breast-conserving surgery and WBRT. Design, Setting, and Participants This retrospective analysis pooled deidentified patient-level data from 10 academic institutions in the United States, Canada, and France from January 1, 1980, through December 31, 2010. All patients had newly diagnosed pure DCIS (no microinvasion), underwent breast-conserving surgery, and received WBRT with or without the boost with a minimum of 5 years of follow-up required for inclusion in the analysis. Given the limited events after WBRT, an a priori power analysis was conducted to estimate the DCIS sample size needed to detect the anticipated benefit of the boost. Data were uniformly recoded at the host institution and underwent primary and secondary reviews before analysis. Sample size calculations (ratio of patients who received the boost dose to those who did not, 2:1; α = .05; power = 80%) estimated that 2982 cases were needed to detect a difference of at least 3%. The final analysis included 4131 patients (2661 in the boost group and 1470 in the no-boost group) with a median follow-up of 9 years and media boost dose of 14 Gy. Data were collected from July 2011 through February 2014 and analyzed from March 2014 through August 2015. Interventions Radiotherapy boost vs no boost. Main Outcomes and Measures Ipsilateral breast tumor recurrence. Results The analysis included 4131 patients (median [SD] age, 56.1 [10.9] years; range, 24-88 years). Patients with positive margins, unknown estrogen receptor status, and comedo necrosis were more likely to have received an RT boost. For the entire cohort, the boost was significantly associated with lower IBTR (hazard ratio [HR], 0.73; 95% CI, 0.57-0.94; P = .01) and with IBTR-free survival (boost vs no-boost groups) of 97.1% (95% CI, 0.96-0.98) vs 96.3% (95% CI, 0.95-0.97) at 5 years, 94.1% (95% CI, 0.93-0.95) vs 92.5% (95% CI, 0.91-0.94) at 10 years, and 91.6% (95% CI, 0.90-0.93) vs 88.0% (95% CI, 0.85-0.91) at 15 years. On multivariable analysis accounting for confounding factors, the boost remained significantly associated with reduced IBTR (HR compared with no boost, 0.68; 95% CI, 0.50-0.91; P = .01) independent of age and tamoxifen citrate use. Conclusions and Relevance This patient-level analysis suggests that the RT boost confers a statistically significant benefit in decreasing IBTR across all DCIS age groups, similar to that seen in patients with invasive breast cancer. These findings suggest that a DCIS RT boost to the tumor bed could be considered to provide an added incremental benefit in decreasing IBTR after a shared discussion between the patient and her radiation oncologist.