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

Standard chemoradiation for high-risk non-metastatic anal squamous cell carcinoma typically requires approximately 27 to 30 fractions of radiation delivered over 5.5 to 6 weeks with concurrent chemotherapy. While effective, this prolonged treatment course creates substantial logistical burden for patients and caregivers, particularly for those living in rural regions with limited access to radiation oncology facilities.

This phase 2, single-arm study evaluates a shortened hypofractionated chemoradiation approach designed to reduce treatment duration while maintaining biologically comparable tumor-directed dosing relative to conventional treatment regimens. The investigational radiation regimen uses a simultaneous integrated boost (SIB) approach delivering 23 fractions over approximately 4.5 weeks, with reduced elective nodal dosing and concurrent standard-of-care chemotherapy consisting of mitomycin C and capecitabine.

The study focuses on patients with high-risk non-metastatic anal squamous cell carcinoma, including larger primary tumors and/or node-positive disease, a population for whom treatment de-escalation strategies are generally not appropriate. The primary objective is to evaluate whether this shortened regimen achieves an acceptable 6-month complete clinical response rate. Secondary objectives include assessment of survival outcomes, disease control, treatment interruptions, clinician- and patient-reported toxicity, quality of life, and treatment burden.

Exploratory correlative analyses will evaluate circulating tumor DNA (ctDNA) collected at protocol-specified time points to assess correlations between circulating biomarkers and clinical outcomes. The study also includes optional qualitative patient and caregiver interviews to better understand treatment experience and logistical burden associated with cancer therapy.

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