The risk of colorectal cancer (CRC) is significant among cancer survivors treated with abdominal radiation therapy (RT). Further, CRC is once of the few cancers for which there is effective screening. Although some expert groups recommend early CRC screening for patients with prior abdominal RT, the effectiveness of early screening is unknown. It is also unknown if radiation-induced CRC passes through a "pre-clinical" phase in which precancerous polyps are detectable and treatable prior to becoming invasive cancers. This study will evaluate whether screening will detect pre-invasive colorectal polyps among survivors treated with RT.

Cancer survivors meeting the COG criteria for CRC screening will undergo colonoscopy and removal of colorectal polyps. Documentation of polyp number, location and pathologic characteristics will be made. Clinical data information will also be collected at the time of patient enrollment.

Inclusion Criteria:

1. Asymptomatic survivors treated with ≥ 25Gy to the abdomen, pelvis or spine, or ≥ 12Gy total body radiation therapy, or ≥ 12Gy whole abdominal RT.
2. Patients who have passed ≥10 years following RT
3. Patients whose current age is 35-49.

Exclusion Criteria:

1. Patients with signs/symptoms suggestive of CRC or other high-risk features such as:

   • Persistent constipation for >2 weeks in the last month
   • One or more unexplained episodes of red blood in the stool in the last month
   • One or more unexplained episodes of black stool in the last month
   • Unexplained pelvic pain in the last month

2. Patients with a history of Crohn's disease or ulcerative colitis

3. Patients already taking part in a colorectal screening program defined as any colorectal screening (colonoscopy, sigmoidoscopy, fecal occult blood test) within last 5 years.

4. Patients with self-reported history of colorectal polyps.

Patients who have received radiation treatment to the abdomen,pelvis or spine.