What age should you begin screening for breast cancer, cervical cancer or colorectal cancer? Read the two-page HINTS Brief #3 by the National Cancer Institute. It addresses when to get a mammogram, pap test, or one of the tests for colorectal cancer such as fecal occult blood tests, barium enema, sigmoidoscopy or colonoscopy. A large segment of men and women failed to identify the correct ages. Updated August 2006. Information may be dated, so it is useful to also check the USPSTF (US Preventive Services Task Force) recommendations for the latest guidelines.