Regorafenib is a medication used to treat cancer. It belongs to a group of drugs called kinase inhibitors, which work by blocking certain proteins that help cancer cells grow and spread. In this trial, it is being studied as a treatment for rectal cancer.

Nivolumab is an immunotherapy medication that helps the body’s immune system fight cancer cells. It works by blocking a protein called PD-1, which normally prevents T-cells (immune system cells) from attacking cancer cells. By blocking PD-1, nivolumab helps the immune system recognize and destroy cancer cells.

Short-course radiotherapy (SCRT) is a type of radiation therapy that delivers targeted radiation to kill cancer cells over a shorter period than traditional radiotherapy. It is a standard treatment approach used before surgery in rectal cancer patients to help shrink the tumor and make it easier to remove during surgery.

Rectal Cancer – A type of cancer that begins in the rectum, which is the last several inches of the large intestine. The disease typically develops from small growths called polyps that form on the inner wall of the rectum. Over time, these polyps can become cancerous and grow into the deeper layers of the rectal wall. In stage II-III (locally advanced), the cancer has grown through the wall of the rectum and may spread to nearby tissues or lymph nodes, but has not spread to distant parts of the body. The condition often develops slowly, and early stages may not cause noticeable symptoms. The disease is part of a larger group of colorectal cancers, which affect the lower digestive system.