Shortening Radiation Course Duration Using Simultaneous Integrated Boost With Lower Intensity Elective Nodal Dosing and Concurrent Chemotherapy for High-Risk Anal Squamous Cell Carcinoma

This phase 2 single-arm study will evaluate whether a shortened course of mildly hypofractionated radiation therapy given with standard concurrent chemotherapy (mitomycin C and capecitabine) can provide acceptable tumor control in patients with high-risk non-metastatic anal squamous cell carcinoma. Standard chemoradiation for anal cancer typically requires approximately 5.5 to 6 weeks of daily radiation, which can create substantial logistical burden for patients and caregivers, particularly those in rural settings. The investigational approach uses a 23-fraction radiation regimen designed to shorten treatment duration while maintaining biologically equivalent tumor-directed dosing compared with standard treatment. The primary question is whether this shorter chemoradiation regimen can achieve an acceptable 6-month complete clinical response rate while maintaining manageable toxicity.

Inclusion Criteria: * Age 18 years or older * Histologically or cytologically confirmed non-metastatic anal squamous cell carcinoma meeting one of the following criteria: T2 tumor measuring ≥4 cm T3 or T4 disease Any node-positive disease * Patients with HPV-associated (p16-positive) perianal cancer are eligible if the tumor extends to the anal verge * Karnofsky Performance Status \>60 * Creatinine clearance \>30 mL/min * Considered by the investigator to be appropriate candidates for concurrent capecitabine and mitomycin C chemotherapy * Ability to understand and willingness to provide informed consent * For participants of childbearing potential: negative pregnancy test or documented absence of pregnancy per institutional standard within 14 days prior to registration * Participants of reproductive potential must agree to use adequate contraception during study treatment and for 90 days after completion of therapy Exclusion Criteria: * Prior pelvic radiation therapy * Uncontrolled intercurrent illness that, in the opinion of the investigator, would prevent safe receipt of radiation therapy or capecitabine * Prior or concurrent malignancy that, in the opinion of the investigator, could interfere with assessment of safety or efficacy * Current receipt of another investigational agent for treatment of anal squamous cell carcinoma