This clinical trial is focused on studying the treatment of rectal cancer, a type of cancer that affects the last part of the large intestine. The study aims to evaluate a personalized approach to managing this disease after a positive response to initial chemotherapy. The treatment involves several medications, including Oxaliplatin, Fluorouracil, Irinotecan Hydrochloride, Capecitabine, and Calcium Folinate. These medications are commonly used in chemotherapy, which is a treatment method that uses drugs to kill cancer cells.

The purpose of the study is to assess whether a less intensive treatment strategy can be effective for patients who respond well to initial chemotherapy. The study will be conducted in two phases. In the first phase, the focus is on ensuring that the cancer can be surgically removed with a high success rate. In the second phase, the study will look at maintaining the current rate of patients remaining free from cancer for three years. Participants will receive treatment over a period of up to 12 months, with some medications given as infusions, which means they are delivered directly into the bloodstream, and others taken orally as tablets.

Throughout the study, various aspects will be monitored, such as the rate of successful surgeries, the ability to preserve the anal sphincter, and the overall response to treatment. The study will also evaluate the quality of life of participants, including digestive, urinary, and sexual functions, using questionnaires. The safety of the chemotherapy treatments will be assessed using a standard scale to ensure that any side effects are carefully managed. The study is expected to continue until November 2030, with the aim of providing valuable insights into the management of rectal cancer.