Technical note: A comparison of in-house 3D-printed and commercially available patient-specific skin collimators for use with electron beam therapy.

PURPOSE: Skin collimation is a useful tool in electron beam therapy (EBT) to decrease the penumbra at the field edge and minimize dose to nearby superficial organs at risk (OARs), but manually fabricating these collimation devices in the clinic to conform to the patient's anatomy can be a difficult and time intensive process. This work compares two types of patient-specific skin collimation (in-house 3D printed and vendor-provided machined brass) using clinically relevant metrics. METHODS: Attenuation measurements were performed to determine the thickness of each material needed to adequately shield both 6 and 9 MeV electron beams. Relative and absolute dose planes at various depths were measured using radiochromic film to compare the surface dose, flatness, and penumbra of the different skin collimation materials. RESULTS: Clinically acceptable thicknesses of each material were determined for both 6 and 9 MeV electron beams. Field width, flatness, and penumbra results between the two systems were very similar and significantly improved compared to measurements performed with no surface collimation. CONCLUSION: Both skin collimation methods investigated in this work generate sharp penumbras at the field edge and can minimize dose to superficial OARs compared to treatment fields with no surface collimation. The benefits of skin collimation are greatest for lower energy electron beams, and the benefits decrease as the measurement depth increases. Using bolus with skin collimation is recommended to avoid surface dose enhancement seen with collimators placed on the skin surface. Ultimately, the appropriate choice of material will depend on the desire to create these devices in-house or outsource the fabrication to a vendor.

Prompt Pain Relief From Bone Metastases: The Virtual Simulation Program.

Purpose: Rapid pain relief for patients with bone metastases can be a challenge due to the lengthy and complex radiation therapy workflow. The purpose of this study was to evaluate the time (in days) between initial radiation oncology consultation and start of palliative radiation treatment after implementing an alternative virtual simulation palliative workflow. Methods and Materials: Patients meeting strict criteria were selected for virtual simulation, which included only those with painful bone metastases who were recommended palliative radiation therapy using standard anterior-posterior/posterior-anterior or opposed lateral fields. A recent (within 30 days) diagnostic computed tomography (CT) scan clearly visualizing the target volume was required for treatment planning. For comparison, a reference group of 40 consecutive patients with bone metastases who underwent in-person CT simulation before virtual simulation implementation was reviewed. Results: Forty-five patients were treated for painful bone metastases as part of the virtual simulation program from May 2021 to October 2022. Regarding travel distance, 23 patients lived locally (<50 miles from the treatment center) and 22 patients were distant (≥50 miles from the treatment center). Average time from consultation to treatment for all patients undergoing virtual simulation was 3.7 days, compared with 7.5 days for patients undergoing in-person CT simulation (3.8 days sooner, on average; P ≤ .001). Before full implementation of the virtual simulation program, 5 eligible patients participated in a virtual simulation pilot from April 2021 to May 2021, in which each patient was contoured and planned on both a pre-existing diagnostic CT scan and a standard CT simulation scan. For virtual simulation-based plans, the average V90, V95, and V99 were 99.99%, 99.87%, and 96.70%. No significant planning target volume (PTV) coverage difference was found on subsequent in-person CT simulation scans. Conclusions: The virtual simulation program decreased the time from consultation to start of treatment by more than 50% for patients recommended palliative radiation therapy for painful bone metastases. This benefit was most significant for outpatients traveling ≥50 miles for treatment. Virtual simulation-based planning can be considered for patients anxious to proceed with radiation therapy quickly or in underserved settings with limited transportation options to regional treatment centers.

Carbon Ion Radiotherapy: An Evidence-Based Review and Summary Recommendations of Clinical Outcomes for Skull-Base Chordomas and Chondrosarcomas.

Skull-base chordoma and chondrosarcoma are rare radioresistant tumors treated with surgical resection and/or radiotherapy. Because of the established dosimetric and biological benefits of heavy particle therapy, we performed a systematic and evidence-based review of the clinical outcomes of patients with skull-base chordoma and chondrosarcoma treated with carbon ion radiotherapy (CIRT). A literature review was performed using a MEDLINE search of all articles to date. We identified 227 studies as appropriate for review, and 24 were ultimately included. The published data illustrate that CIRT provides benchmark disease control outcomes for skull-base chordoma and chondrosarcoma, respectively, with acceptable toxicity. CIRT is an advanced treatment technique that may provide not only dosimetric benefits over conventional photon therapy but also biologic intensification to overcome mechanisms of radioresistance. Ongoing research is needed to define the magnitude of benefit, patient selection, and cost-effectiveness of CIRT compared to other forms of radiotherapy.

Targeting KRAS in pancreatic adenocarcinoma: Progress in demystifying the holy grail.

Pancreatic cancer (PC) remains one of the most challenging diseases, with a very poor 5-year overall survival of around 11.5%. Kirsten rat sarcoma virus (KRAS) mutation is seen in 90%-95% of PC patients and plays an important role in cancer cell proliferation, differentiation, metabolism, and survival, making it an essential mutation for targeted therapy. Despite extensive efforts in studying this oncogene, there has been little success in finding a drug to target this pathway, labelling it for decades as "undruggable". In this article we summarize some of the efforts made to target the KRAS pathway in PC, discuss the challenges, and shed light on promising clinical trials.

Future Perspective: Carbon Ion Radiotherapy for Head and Neck and Skull Base Malignancies.

Head and neck and base of skull malignancies are challenging for surgical and radiotherapy treatment due to the density of sensitive tissues. Carbon ion radiotherapy (CIRT) is a form of heavy particle therapy that uses accelerated carbon ions to treat malignancies that may be radioresistant or in challenging anatomic locations. CIRT has an increased biological effectiveness (ie, increased cell killing) at the end of the range of the carbon beam (ie, within the target tissue) but not in the entrance dose. This increased biological effectiveness can overcome the effects of radioresistant tumors, tissue hypoxia, and the need for radiotherapy fractionation.

Proton Therapy With Concurrent Chemotherapy for Thoracic Esophageal Cancer: Toxicity, Disease Control, and Survival Outcomes.

Purpose: When treating esophageal cancer with radiation therapy, it is critical to limit the dose to surrounding structures, such as the lung and/or heart, as much as possible. Proton radiation therapy allows a reduced radiation dose to both the heart and lungs, potentially reducing the risk of cardiopulmonary toxicity. Here, we report disease control, survival, and toxicity outcomes among patients with esophageal cancer treated with proton radiation therapy and concurrent chemotherapy (chemoradiation therapy; CRT) with or without surgery. Materials and Methods: We enrolled 17 patients with thoracic esophageal carcinoma on a prospective registry between 2010 and 2021. Patients received proton therapy to a median dose of 50.4-GyRBE (range, 50.4-64.8) in 1.8-Gy fractions.Acute and late toxicities were graded per the Common Terminology Criteria for Adverse Events, version 4.0 (US National Cancer Institute, Bethesda, Maryland). In addition, disease control, patterns of failure, and survival outcomes were collected. Results: Nine patients received preoperative CRT, and 8 received definitive CRT. Overall, 88% of patients had adenocarcinoma, and 12% had squamous cell carcinoma. With a median follow-up of 2.1 years (range, 0.5-9.4), the 3-year local progression-free, disease-free, and overall survival rates were 85%, 66%, and 55%, respectively. Two patients (1 with adenocarcinoma and 1 with squamous cell carcinoma) recurred at the primary site after refusing surgery after a complete clinical response to CRT. The most common acute nonhematologic and hematologic toxicities, respectively, were grades 1 to 3 esophagitis and grades 1 to 4 leukopenia, both affecting 82% of patients. No acute cardiopulmonary toxicities were observed in the absence of surgical resection. Reagarding surgical complications, 3 postoperative cardiopulmonary complications occurred as follows: 1 grade 1 pleural effusion, 1 grade 3 pleural effusion, and 1 grade 2 anastomotic leak. Two severe late CRT toxicities occurred: 1 grade 5 tracheoesophageal fistula and 1 grade 3 esophageal stenosis requiring a feeding tube. Conclusion: Proton radiation therapy is a safe, effective treatment for esophageal cancer with increasing evidence supporting its role in reducing cardiopulmonary toxicity.

Patterns-of-care disparities among uninsured versus insured patients with anorectal carcinoma referred for radiotherapy at an Urban Safety-Net Hospital.

Background: To compare patterns-of-care and clinical outcomes among uninsured versus insured patients (IPs) with anorectal malignancies referred for radiotherapy at an urban safety-net hospital. This topic is important because uninsured patients (UPs) in the US often have limited access to health care, which can result in worse health outcomes. Methods: We reviewed the medical records of 59 patients with biopsy-proven, non-metastatic anal and rectal cancers who received curative-intent primary or neoadjuvant/adjuvant radiotherapy between May 2002 and August 2012. Data regarding patient and disease characteristics, weight loss, insurance status at symptom onset, date of first therapeutic intervention, and survival status at last follow-up, were collected and analyzed. Results: The percentage of IPs presenting with T4 tumors was 7% versus 40% among the uninsured (P=0.005). The median interval between first symptom onset and diagnosis date was 89 (range, 0-1,428) days for IPs and 221 (range, 0-1,576) days for UPs (P=0.01). The median interval between first symptom onset and treatment initiation was 172 (range, 9-1,498) days for IPs and 302 (range, 35-1,624 days) days for UPs (P=0.01). The 5-year overall survival rate was 59% for the entire cohort, 62% for the insured patients, and 55% for the uninsured patients (P=0.76). Conclusions: Differences in health insurance status demonstrated various disparities in patterns-of-care, including significant delay in diagnosis, more advanced-stage disease at presentation, and treatment initiation delays among UPs. Nevertheless, overall survival at 5 years was not statistically significant between the insured and the uninsured.

Dose-escalated proton therapy with elective nodal irradiation and concomitant chemotherapy for unresectable, borderline resectable, or medically inoperable pancreatic cancer: a phase II trial.

Background: To report outcomes of a phase II single-institution trial of dose-escalated proton radiotherapy with elective nodal irradiation (ENI) and concomitant chemotherapy for patients with unresectable, borderline resectable, or medically inoperable pancreatic adenocarcinoma. Methods: Patients received 40.5 GyRBE in 18 fractions to the gross disease and elective nodal volumes followed by 22.5 GyRBE as a 10-fraction boost to the gross disease for a cumulative dose of 63 GyRBE over 28 fractions. Oral capecitabine (1,000 mg taken orally twice daily) was given on radiation treatment days. The primary objective of this study was to improve the proportion surviving to at least 1 year from the historical rate of 50% to 75%. Secondary objectives included assessing gastrointestinal (GI) toxicity and weight loss during treatment, and evaluating the safety of subsequent surgical resection. This single-institution study was closed to accrual early after the opening of the multicenter PAN009-18 trial by the Proton Collaborative Group (PCG), which follows a similar protocol. Results: At enrollment, 10 (67%) patients had unresectable disease, 3 (20%) had borderline-resectable disease, and 2 (13%) refused surgery. All 15 patients successfully completed radiation therapy as prescribed. With regard to toxicity, a single patient experienced grade 3 nausea requiring cessation of capecitabine, which ultimately resolved by treatment completion. The median percentage weight loss during treatment was -3.0% (range, -9.6% to +12.0%). Two (13%) initially borderline patients ultimately underwent R0 resection: their total operating room times were 267 and 410 minutes, and blood loss was 700 and 400 mL, respectively. Neither patient experienced intraoperative or postoperative complications. Both were discharged on postoperative day 6. The median follow-up was 0.93 years (range, 0.21 to 2.14 years). The 1-year overall survival (OS) rate was 47%. Three enrolled patients are currently alive: 2 with no evidence of disease and 1 with stable disease. Conclusions: The primary objective of 1-year OS of 75% was not reached. Proton therapy was well-tolerated. Patients undergoing surgery did not experience operative or perioperative complications, suggesting that patients with borderline resectable or even resectable disease may benefit from neoadjuvant proton therapy. The PCG will test this premise as patients accrue to the multicenter PAN009-18 trial. Trial Registration: NCT02598349.

The incidence of brainstem toxicity following high-dose conformal proton therapy for adult skull-base malignancies.

BACKGROUND: Dose escalation for skull-based malignancies often presents risks to critical adjacent neural structures, including the brainstem. We report the incidence of brainstem toxicity following fractionated high-dose conformal proton therapy and associated dosimetric parameters. MATERIAL AND METHODS: We performed a single-institution review of patients with skull-base chordoma or chondrosarcoma who were treated with proton therapy between February 2007 and January 2020 on a prospective outcomes-tracking protocol. The primary endpoint was grade ≥2 brainstem toxicity. No patients received concurrent chemotherapy, and brainstem toxicity was censored for analysis if it coincided with local disease progression. RESULTS: We analyzed 163 patients who received a minimum of 45 GyRBE to 0.03 cm3 of the brainstem. Patients were treated to a median total dose of 73.8 (range 64.5-74.4) GyRBE at 1.8 GyRBE per fraction with 17 patients undergoing twice-daily treatment at 1.2 GyRBE per fraction. With a median follow-up of 4 years, the 5-year cumulative incidence of grade ≥2 brainstem injury was 1.3% (95% CI 0.25-4.3%). There was one grade 2, one grade 3, and no grade 4 or 5 events, with all patients recovering function with medical management. CONCLUSION: In delivering curative-intent radiotherapy for skull-base chordoma and chondrosarcoma in adults, small volumes of the brainstem can safely receive at least 64 GyRBE with minimal risk of serious brainstem injury.

Impact of Type of Treatment Center and Access to Care on Mortality and Survival for Skull Base Chordoma and Chondrosarcoma.

Introduction In adults with skull base chordoma or chondrosarcoma, the impact of treatment center and access to care have not been well described in regard to perioperative mortality and survival. Methods A query of the National Cancer Database (NCDB) and review of 1,102 adults-488 with chordomas and 614 with chondrosarcomas-was performed. The Kaplan-Meier's product limit method and chi-square analysis, respectively, assessed overall survival and 30-day (30D) and 90-day (90D) mortalities. Results For 925 patients who had surgery and available mortality data, the 30D and 90D mortality rates were 0.9 and 1.5%. Lower education level ( p = 0.0185) and treatment at a nonacademic facility ( p = 0.016) were associated with increased risk of 90-day mortality. Median follow-up was 52 months and analysis was dichotomized by histology. For those with skull base chordoma, patients from a larger metro size ( p = 0.002), age below the median 52 years ( p ≤ 0.001), and private insurance (<0.001) were associated with prolonged survival, whereas for skull base chondrosarcoma, the factors were treatment at an academic medical center ( p = 0.001), high-volume center ( p = 0.007), age below the median 52 years ( p ≤ 0.001), higher income ( p = 0.043), higher education ( p = 0.017), and private insurance ( p ≤ 0.001). Comparing high-, medium-, and low-volume centers, high-volume centers were most likely to be academic, deliver radiotherapy, escalate doses >70 Gy, and utilize proton radiotherapy consistent across both disease subsets. Conclusion Higher educational attainment and treatment at an academic facility were associated with decreased 90D mortality for patients with skull base chordoma and chondrosarcoma. For those with skull base chordoma, larger metro size, younger age, and private insurance were associated with prolonged survival; for those with chondrosarcoma, it was treatment at a high-volume or academic medical center, younger age, higher income or education, and private insurance.

Hyperfractionated-Accelerated Reirradiation with Proton Therapy for Radiation-Associated Breast Angiosarcoma.

Purpose: Radiation-associated angiosarcoma (RAAS) is a rare complication among patients treated with radiation therapy for breast cancer. Hyperfractionated-accelerated reirradiation (HART) improves local control after surgery. Proton therapy may further improve the therapeutic ratio by mitigating potential toxicity. Materials and Methods: Six patients enrolled in a prospective registry with localized RAAS received HART with proton therapy between 2015 and 2021. HART was delivered twice or thrice daily in fraction sizes of 1.5 or 1.0 Gy, respectively. All patients received 45 Gy to a large elective volume followed by boosts to a median dose of 65 (range, 60-75) Gy. Toxicity was recorded prospectively by using the Common Terminology Criteria for Adverse Events, version 4.0. Results: The median follow-up duration was 1.5 (range, 0.25-2.9) years. The median age at RAAS diagnosis was 73 (range, 60-83) years with a median latency of 8.9 (range, 5-14) years between radiation therapy completion and RAAS diagnosis. The median mean heart dose was 2.2 (range, 0.1-4.96) Gy. HART was delivered postoperatively (n = 1), preoperatively (n = 3), preoperatively for local recurrence after initial management with mastectomy (n = 1), and as definitive treatment (n = 1). All patients had local control of disease throughout follow-up. Three of 4 patients treated preoperatively had a pathologic complete response. The patient treated definitively had a complete metabolic response on her posttreatment PET/CT (positron emission tomography-computed tomography) scan. Two patients developed distant metastatic disease despite local control and died of their disease. Acute grade 3 toxicity occurred in 3 patients: 2 patients undergoing preoperative HART experienced wound dehiscence and 1 postoperatively developed grade 3 wound infection, which resolved. Conclusion: HART with proton therapy appears effective for local control of RAAS with a high rate of pathologic complete response and no local recurrences to date. However, vigilant surveillance for distant metastasis should occur. Toxicity is comparable to that in photon/electron series. Proton therapy for RAAS may maximize normal tissue sparing in this large-volume reirradiation setting.

Disease Control after Radiotherapy for Adult Craniopharyngioma: Clinical Outcomes from a Large Single-Institution Series.

PURPOSE: To report disease control and treatment-related side effects among adult patients with craniopharyngioma treated with radiotherapy. METHODS: We performed a single-institution review of adult patients (> 21 years old) with craniopharyngioma treated with radiotherapy either definitively or postoperatively for gross residual disease. We report disease control, survival, and radiotherapy-related side effects. RESULTS: A total of 49 adult patients with craniopharyngioma were included, 27 of whom were treated at initial presentation and 22 for recurrent disease following initial surgery and observation. Overall, 77% received radiotherapy postoperatively (either after primary surgery or surgery for recurrence). With a median clinical and radiographic follow-up of 4.2 (range, 0.4-21.6) years and 3.0 (range, 0-21.5) years, the 5- and 10-year local control rates were 100 and 94%, respectively. The 5- and 10-year overall survival rates were 80 and 66%, respectively. Eleven percent of patients experienced grade 2 vision deterioration and 18% suffered grade 2 endocrinopathies following radiotherapy. CONCLUSIONS: Radiotherapy provides excellent disease control with acceptable toxicity among adult patients with craniopharyngioma. These data support the use of fractionated radiotherapy in adult patients with recurrent or gross residual disease after surgery. For inoperable patients or those with moderate or high surgical risk to neurologic and/or vascular structures, we advocate for limited surgical resection and postoperative radiotherapy to balance optimal tumor control with tumor- and treatment-related morbidity.

Current Advances in the Management of Adult Craniopharyngiomas.

Craniopharyngiomas (CPs) are slow growing, histologically benign intracranial tumors located in the sellar-suprasellar region. Although known to have low mortality, their location and relationship to the adjacent neural structures results in patients having significant neurologic, endocrine, and visual comorbidities. The invasive nature of this tumor makes complete resection a challenge and contributes to its recurrence. Additionally, these tumors are bimodally distributed, being treated with surgery, and are followed by other adjuncts, such as focused radiation therapy, e.g., Gamma knife. Advances in surgical techniques, imaging tools, and instrumentations have resulted in the evolution of surgery using endoscopic techniques, with residual components being treated by radiotherapy to target the residual tumor. Advances in molecular biology have elucidated the main pathways involved in tumor development and recurrence, but presently, no other treatments are offered to patients, besides surgery, radiation, and endocrine management, as the disease and tumor evolve. We review the contemporary management of these tumors, from the evolution of surgical treatments, utilizing standard open microscopic approaches to the more recent endoscopic surgery, and discuss the current recommendations for care of these patients. We discuss the developments in radiation therapy, such as radiosurgery, being used as treatment strategies for craniopharyngioma, highlighting their beneficial effects on tumor resections while decreasing the rates of adverse outcomes. We also outline the recent chemotherapy modalities, which help control tumor growth, and the immune landscape on craniopharyngiomas that allow the development of novel immunotherapies.

Treatment of Uveal Melanoma With Radioactive Iodine 125 Implant Compared With Proton Beam Radiotherapy.

OBJECTIVE: To review the current state of radiation therapy for uveal melanoma and compare particle radiation and brachytherapy. PATIENTS AND METHODS: The medical records of 156 patients treated for uveal melanoma between May 30, 2012, and March 16, 2020, were retrospectively reviewed. Treatments consisted of either radioactive iodine 125 implant (RAI) or fractionated proton radiation (proton beam therapy [PBT]). Baseline characteristics were compared using a Wilcoxon rank sum test or χ2 test. Outcomes were compared using Cox proportional hazards regression models or logistic regression models. RESULTS: The median length of follow-up after treatment was 2.7 years (range, 0.5 to 9.0 years). Patients who underwent treatment with RAI were older (median age, 67 vs 59 years; P<.001) and had a lower tumor classification (American Joint Commission on Cancer; P=.001) compared with those who underwent PBT. There was no significant difference between RAI and PBT in the outcomes of liver metastases, death, enucleation, tearing, vision loss, retinal detachment, tumor thickness, conjunctivitis, optic neuropathy, iris neovascularization, or neovascular glaucoma (all P>.05). Patients who underwent RAI treatment had significantly higher risk of diplopia (P<.001), cataract progression (P<.001), and maculopathy (P=.03) compared with those who received PBT. Patients who underwent RAI were at higher risk of eyelash loss (P=.006) compared with the PBT group. CONCLUSION: Treatment with PBT and RAI has similar efficacy; however, there are differences in the adverse outcomes associated with these 2 modalities.

Current Management and Image Review of Skull Base Chordoma: What the Radiologist Needs to Know.

Chordomas of the skull-base are typically slow-growing, notochord-derived tumors that most commonly originate along the clivus. Skull base chordoma is treated with surgery and radiotherapy. Local recurrence approaches 50% at 10 years. Radiologists play a critical role in diagnosis, treatment planning, and follow-up. Surgeons and radiation oncologists rely on radiologists for pre-operative delineation of tumor and adjacent anatomy, identification of post-treatment changes and disease recurrence, and radiation treatment effects. This review provides an overview of clinical characteristics, surgical anatomy, indications for radiotherapy, identification of treatment complications, and patterns of disease recurrence for radiologists to provide value in the management of these lesions.

Clinical Outcomes Following Dose-Escalated Proton Therapy for Skull-Base Chordoma.

PURPOSE: To evaluate the effectiveness of external-beam proton therapy (PT) on local control and survival in patients with skull-base chordoma. MATERIALS AND METHODS: We reviewed the medical records of patients with skull-base chordoma treated with definitive or adjuvant high-dose PT and updated their follow-up when feasible. We assessed overall survival, disease-specific survival, local control, and freedom from distant metastasis. Radiotherapy toxicities were scored using the Common Terminology Criteria for Adverse Events, version 4.0. RESULTS: A total 112 patients were analyzed, of whom 105 (94%) received PT and 7 (6%) received combined proton-photon therapy between 2007 and 2019. Eighty-seven patients (78%) underwent a subtotal resection, 22 (20%) a gross total resection, and 3 (3%) a biopsy alone. The median radiotherapy dose was 73.8 Gy radiobiologic equivalent (GyRBE; range, 69.6-74.4). Ninety patients (80%) had gross disease at radiotherapy and 7 (6%) were treated for locally recurrent disease following surgery. Median follow-up was 4.4 years (range, 0.4-12.6); for living patients, it was 4.6 years (range, 0.4-12.6), and for deceased patients, 4.1 years (range, 1.2-11.2). At 5 years after radiotherapy, the actuarial overall survival, disease-specific survival, local control, and freedom from distant metastasis rates were 78% (n = 87), 83% (n = 93), 74% (n = 83), and 99% (n = 111), respectively. The median time to local progression was 2.4 years (range, 0.8-7). Local control and disease-specific survival by resection status was 95% versus 70% (P = 0.28) and 100% versus 80% (P = 0.06) for gross total, versus subtotal, resection or biopsy alone, respectively. There were no serious acute toxicities (grade ≥ 3) related to radiotherapy. CONCLUSION: High-dose PT alone or after surgical resection for skull-base chordoma reaffirms the favorable 5-year actuarial local control rate compared with conventional techniques with acceptable late-complication-free survival. Outcomes following gross total resection and adjuvant PT were excellent. Further follow-up of this cohort is necessary to better characterize long-term disease control and late toxicities.

Proton therapy for adult medulloblastoma: Acute toxicity and disease control outcomes.

PURPOSE: We report disease control, survival outcomes, and treatment-related toxicity among adult medulloblastoma patients who received proton craniospinal irradiation (CSI) as part of multimodality therapy. METHODS: We reviewed 20 adults with medulloblastoma (≥ 22 years old) who received postoperative proton CSI ± chemotherapy between 2008 and 2020. Patient, disease, and treatment details and prospectively obtained patient-reported acute CSI toxicities were collected. Acute hematologic data were analyzed. RESULTS: Median age at diagnosis was 27 years; 45% of patients had high-risk disease; 75% received chemotherapy, most (65%) after CSI. Eight (40%) patients received concurrent vincristine with radiotherapy. Median CSI dose was 36GyE with a median tumor bed boost of 54GyE. Median duration of radiotherapy was 44 days. No acute ≥ grade 3 gastrointestinal or hematologic toxicities attributable to CSI occurred. Grade 2 nausea and vomiting affected 25% and 5% of patients, respectively, while 36% developed acute grade 2 hematologic toxicity (36% grade 2 leukopenia and 7% grade 2 neutropenia). Those receiving concurrent chemotherapy with CSI had a 38% rate of grade 2 hematologic toxicity compared to 33% among those not receiving concurrent chemotherapy. Among patients receiving adjuvant chemotherapy (n = 13), 100% completed ≥ 4 cycles and 85% completed all planned cycles. With a median follow-up of 3.1 years, 4-year actuarial local control, disease-free survival, and overall survival rates were 90%, 90%, and 95%, respectively. CONCLUSIONS: Proton CSI in adult medulloblastoma patients is very well tolerated and shows promising disease control and survival outcomes. These data support the standard use of proton CSI for adult medulloblastoma.