Faculty Bibliography

BACKGROUND:In the present study, we assessed the effect of prostate gland size on patient-assessed genitourinary and gastrointestinal (GI) quality of life (QOL) after definitive treatment of prostate adenocarcinoma with proton beam therapy. PATIENTS AND METHODS:(volume of organ receiving x Gy), and patient-reported QOL at 6 months. Genitourinary QOL was assessed using the American Urological Association symptom score and EPIC urinary domain score. GI QOL was assessed using the EPIC GI domain score. RESULTS:, -0.55; P = .67). CONCLUSION:Definitive proton beam therapy for prostate cancer to a dose of 79.2 Gy resulted in excellent patient-reported urinary and GI QOL, independently of the baseline prostate size. This single-institution finding should be tested further in a multi-institutional study to confirm the potential limited role of androgen deprivation therapy.

AIM/OBJECTIVE:Anterior-oblique (AO) proton beams can form an attractive option for prostate patients receiving external beam radiotherapy (EBRT) as they avoid the femoral heads. For a cohort with hydrogel prostate-rectum spacers, we asked whether it was possible to generate AO proton plans robust to end-of-range elevations in linear energy transfer (LET) and modeled relative biological effectiveness (RBE). Additionally we considered how rectal spacers influenced planned dose distributions for AO and standard bilateral (SB) proton beams versus intensity-modulated radiotherapy (IMRT). MATERIAL AND METHODS/METHODS:We studied three treatment strategies for 10 patients with rectal spacers: (A) AO proton beams, (B) SB proton beams and (C) IMRT. For strategy (A) dose and LET distributions were simulated (using the TOPAS Monte Carlo platform) and the McNamara model was used to calculate proton RBE as a function of LET, dose per fraction, and photon α/β. All calculations were performed on pretreatment scans: inter- and intra-fractional changes in anatomy/set-up were not considered. RESULTS:For 9/10 patients, rectal spacers enabled generation of AO proton plans robust to modeled RBE elevations: rectal dose constraints were fulfilled even when the variable RBE model was applied with a conservative α/β = 2 Gy. Amongst a subset of patients the proton rectal doses for the planning target volume plans were remarkably low: for 2/10 SB plans and 4/10 AO plans, ≤10% of the rectum received ≥20 Gy. AO proton plans delivered integral doses a factor of approximately three lower than IMRT and spared the femoral heads almost entirely. CONCLUSION/CONCLUSIONS:Typically, rectal spacers enabled the generation of anterior beam proton plans that appeared robust to modeled variation in RBE. However, further analysis of day-to-day robustness would be required prior to a clinical implementation of AO proton beams. Such beams offer almost complete femoral head sparing, but their broader value relative to IMRT and SB protons remains unclear.

A 33-year-old man with symptomatic, unresectable osteosarcoma of the neck experienced disease progression despite treatment with multiple systemic agents. Given the tumor location, adjacent to the spinal cord and encasing the brachial plexus, proton beam therapy was recommended instead of conventional photon radiation therapy. The treatment was delivered in 3 weekly 10 cobalt-gray equivalents fractions, and there was minimal associated toxicity. There has been significant improvement in the patient's presenting symptoms as well as radiologically stable disease at 1 year. A photon intensity-modulated radiation therapy plan was created retrospectively for dosimetric comparison and demonstrated noninferiority, thereby highlighting the need for judicious use of proton therapy in certain cases.

Craniospinal irradiation is standard radiotherapy (RT) for localized intracranial nongerminoma germ cell tumors (NGGCT). Given its toxicity, there is interest in using smaller fields. We examined outcomes of NGGCT patients receiving reduced-volume RT at a single institution. Records of 16 patients who received reduced-volume RT as part of definitive treatment between 1996 and 2016 were reviewed. Median age at presentation was 10.8 years (range 4.6-41.0 years). Ten patients had pineal tumors and 6 had suprasellar tumors. All received chemotherapy and 9 patients received second-look surgery thereafter. RT volume was tumor-only to a median of 54 Gy (range 50.4-54 Gy) in 3 patients and whole-ventricle irradiation to a median of 30.6 Gy (range 30.6-36 Gy) with a boost to 54 Gy in 13 patients. Median follow-up was 4.1 years (range 1.9-19.3 years). Three patients recurred locally at a median 9.9 months (range 9.6-10.6 months) after diagnosis, and one of these developed leptomeningeal relapse after 30 months. One patient expired from disease 2.6 years post-diagnosis and another due to stroke 19.3 years post-diagnosis. Fourteen patients are alive with no evidence of disease. Kaplan-Meier estimates of the 4-year overall survival and failure-free survival are 92% (95% confidence interval [CI], 57-99%) and 81% (95% CI 53-94%), respectively. Excellent disease control was observed in these patients with no initial relapses outside of these RT fields. The results of ACNS1123 may better delineate patterns of failure and identify subgroups likely to benefit from this approach.

PURPOSE/OBJECTIVE:Reirradiation therapy (re-RT) is the only potentially curative treatment option for patients with locally recurrent head and neck cancer (HNC). Given the significant morbidity with head and neck re-RT, interest in proton beam radiation therapy (PBRT) has increased. We report the first multi-institutional clinical experience using curative-intent PBRT for re-RT in recurrent HNC. METHODS AND MATERIALS/METHODS:A retrospective analysis of ongoing prospective data registries from 2 hybrid community practice and academic proton centers was conducted. Patients with recurrent HNC who underwent at least 1 prior course of definitive-intent external beam radiation therapy (RT) were included. Acute and late toxicities were assessed with the National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0 and the Radiation Therapy Oncology Group late radiation morbidity scoring system, respectively. The cumulative incidence of locoregional failure was calculated with death as a competing risk. The actuarial 12-month freedom-from-distant metastasis and overall survival rates were calculated with the Kaplan-Meier method. RESULTS:Ninety-two consecutive patients were treated with curative-intent re-RT with PBRT between 2011 and 2014. Median follow-up among surviving patients was 13.3 months and among all patients was 10.4 months. The median time between last RT and PBRT was 34.4 months. There were 76 patients with 1 prior RT course and 16 with 2 or more courses. The median PBRT dose was 60.6 Gy (relative biological effectiveness, [RBE]). Eighty-five percent of patients underwent prior HNC RT for an oropharynx primary, and 39% underwent salvage surgery before re-RT. The cumulative incidence of locoregional failure at 12 months, with death as a competing risk, was 25.1%. The actuarial 12-month freedom-from-distant metastasis and overall survival rates were 84.0% and 65.2%, respectively. Acute toxicities of grade 3 or greater included mucositis (9.9%), dysphagia (9.1%), esophagitis (9.1%), and dermatitis (3.3%). There was 1 death during PBRT due to disease progression. Grade 3 or greater late skin and dysphagia toxicities were noted in 6 patients (8.7%) and 4 patients (7.1%), respectively. Two patients had grade 5 toxicity due to treatment-related bleeding. CONCLUSIONS:Proton beam re-RT of the head and neck can provide effective tumor control with acceptable acute and late toxicity profiles likely because of the decreased dose to the surrounding normal, albeit previously irradiated, tissue, although longer follow-up is needed to confirm these findings.