Adaptive Radiotherapy for Locally-Advanced Anal Squamous Cell Carcinoma Treatment

This study focuses on a specific type of cancer, known as HPV-positive locally advanced anal cancer. This is a condition where the tumor is larger than 4 cm, or has spread to the lymph nodes. The standard treatment for this cancer involves radiation therapy and chemotherapy, specifically 5-fluorouracil (5-FU) and mitomycin-C. The radiation therapy is usually given over six weeks. During this time, the tumor often shrinks, which can be seen on weekly scans. However, the treatment plan is typically not adjusted to account for this shrinkage due to various constraints. This study aims to explore a more efficient method, called daily adaptive radiation, which could adjust the treatment plan based on the tumor's current size, potentially improving the treatment process. During the study, participants will receive their usual treatment, but with a key difference. The radiation therapy will be adapted daily based on the tumor's size, using a technique called adaptive radiotherapy. The main goal is to measure how long it takes to plan and deliver each treatment fraction, from the start of the first scan to the end of treatment delivery. This will help determine if daily adaptive radiation is a practical and efficient approach for treating this type of cancer.