Overview Colorectal cancer is the third most common cancer in both men and women. It is treatable when caught early through routine screening tests. Understanding Your Diagnosis A number of tests can be used to diagnose colorectal cancer. These include a fecal occult blood test, a colonoscopy, a sigmoidoscopy, and other tests. Deciding on Treatment Your treatment plans depends on your age and health, and the extent of your disease. You may need surgery, chemotherapy, radiation therapy, biologic therapy, or a combination of these. Managing Side Effects Side effects are common during cancer treatment. Some side effects may change with time, while others stay the same. Your doctor or cancer nurse can suggest ways to ease the side effects you experience.