Linear Energy Transfer (LET)-Optimized Intensity Modulated Proton Therapy (IMPT) as a Component of Definitive Chemoradiation for Newly Diagnosed Squamous Cell Carcinoma of the Anal Canal: a Feasibility Trial

PRIMARY OBJECTIVES: I. To assess physician-reported acute grade 3 or greater gastrointestinal, genitourinary and hematologic toxicities at 12 weeks post-treatment for patients treated with linear energy transfer (LET)-optimized, intensity-modulated proton therapy (IMPT) and compare to contemporary controls treated with volume modulated arc therapy (VMAT) to determine the feasibility of this outcome for a future randomized trial. SECONDARY OBJECTIVES: I. To assess the feasibility of enrolling patients on a prospective trial delivering LET-optimized IMPT for newly diagnosed, non-metastatic anal cancer. II. To develop guidelines and workflow to create and deliver anal canal cancer treatments using LET-optimized IMPT. III. To evaluate complete response rate at 12 weeks and 24 weeks post-treatment. IV. To evaluate local progression free survival, distant metastasis-free survival and overall survival at 24 and 48 months. V. To evaluate rates of patient-reported acute toxicity, function, distress and quality of life (QOL) at 12 weeks. VI. To evaluate rates of patient-reported late toxicity, function, distress and QOL every 6 months for 24 months. VII. To evaluate the value of proton therapy by comparing Time-Driven Activity-Based Costing data from the date of consultation until the date of the 12-week follow up visit post-treatment with contemporary controls treated with VMAT. EXPLORATORY OBJECTIVES: I. To compare dose to the pelvic bone marrow, bowel, bladder and genitalia between LET-optimized IMPT, traditionally-optimized IMPT and VMAT. II. To assess rates of leukopenia, neutropenia and lymphopenia at 12-weeks post-treatment for patients treated with LET-optimized IMPT and compare to contemporary controls treated with VMAT. III. To correlate white blood cell counts (WBC), absolute neutrophil counts (ANC) and absolute lymphocyte counts (ALC) with dose to the pelvic bone marrow for patients treated with LET-optimized IMPT. OUTLINE: Patients undergo linear energy transfer-optimized intensity modulated proton therapy 5 times per week for 5-6 weeks. Patients also receive standard cisplatin and fluorouracil intravenously (IV) weekly for up to 6 weeks in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up at 12 weeks.