Lower-Dose Chemoradiation in Treating Patients With Early-Stage Anal Cancer, the DECREASE Study

PRIMARY OBJECTIVE: I. To determine whether de-intensified chemoradiation for early stage squamous cell carcinoma of the anal canal (SCCA) is able to maintain excellent 2-year disease control of 85% or higher while improving anorectal health-related quality of life (HRQL), compared to standard-dose chemoradiation therapy (CRT), as measured by the change in the Fecal Incontinence Quality of Life scale (FIQoL) instrument coping/behavior domain from baseline to 1 year. SECONDARY OBJECTIVES: I. To compare changes in patient-reported HRQL (as per Fecal Incontinence Severity Index \[FISI\], Patient Reported Outcomes Measurement Information System \[PROMIS\], International Index of Erectile Function \[IIEF\], Sexual Function-Vaginal Changes Questionnaire \[SVQ\], and Vaginal Assessment Scale \[VAS\]/Vulvar Assessment Scale \[VuAS\] instruments) between the experimental and control arm. II. To compare patterns of failure (local and regional relapse versus distant; in-field versus out-of-field of radiation), disease control, and overall survival between experimental and control arm. III. To correlate vaginal dilator use during radiation delivery with sexual function. IV. To measure changes in serum total testosterone from baseline to up to 12 months after radiation. V. To validate the utility of imaging features of inguinal and pelvic lymph nodes obtained prior to treatment as a prognostic indicator that can identify patients with early-stage anal squamous cell carcinoma for whom treatment with de-intensified chemoradiation is appropriate. VI. To determine the incidence of and predictors for cardiovascular toxicity in patients receiving fluorouracil (5-FU) or capecitabine. OUTLINE: Patients are randomized to 1 of 2 arms. ARM A (STANDARD-DOSE CHEMORADIATION): Patients undergo 28 fractions of intensity-modulated radiation therapy (IMRT). Within 24 hours, patients also receive mitomycin intravenously (IV) over 30 minutes or less on day 1 and either fluorouracil IV over 24 hours on days 1-4 and 29-32 or capecitabine orally (PO) twice daily (BID) 5 days per week (Monday - Friday) until completion of IMRT in the absence of disease progression or unacceptable toxicity. ARM B (DE-INTENSIFIED CHEMORADIATION): Patients undergo 20 or 23 fractions of IMRT. Within 24 hours, patients also receive mitomycin IV over 30 minutes or less on day 1 and either fluorouracil IV over 24 hours on days 1-4 or capecitabine PO BID 5 days per week (Monday - Friday) until completion of IMRT in the absence of disease progression or unacceptable toxicity. All patients receive fludeoxyglucose F-18 (FDG) and undergo positron emission tomography (PET)/magnetic resonance imaging (MRI) or receive FDG and undergo PET/computed tomography (CT) during baseline. Patients undergo CT or MRI on the trial. Patients also undergo tissue biopsy during screening and at the discretion of the treating physician. Additionally, patients undergo blood sample collection throughout the trial. After completion of study treatment, patients are followed up at 6 weeks, every 3 months for years 1-2, every 6 months for year 3, then annually for years 4-5.