The rectum is the last several inches of the large intestine. It starts at the end of the final segment of your colon and ends when it reaches the short, narrow passage leading to the anus.Cancer inside the rectum (rectal cancer) and cancer inside the colon (colon cancer) are often referred to together as "colorectal cancer."While rectal and colon cancers are similar in many ways, their treatments are quite different. This is mainly because the rectum sits in a tight space, barely separated from other organs and structures in the pelvic cavity. As a result, complete surgical removal of rectal cancer is challenging and highly complex. Additional treatment is often needed before or after surgery — or both — to reduce the chance that the cancer will return.In the past, long-term survival was uncommon for people with rectal cancer, even after extensive treatment. Thanks to treatment advances over the past 30 years, rectal cancer can now, in many cases, be cured.