(Associated Press) -- Several doctors groups and advocacy groups set guidelines for cancer screening, and they update that advice periodically as new information emerges. Sometimes they agree, sometimes they don't. Last year, a number of groups got together and issued consensus guidelines for colon cancer.

The U.S. Preventive Services Task Force, a government-appointed, independent panel of doctors and scientists, also makes recommendations looked to by doctors groups, insurers and policy makers.

The latest advice from the major medical groups for routine screening -- primarily for people who don't have a family history of a particular cancer or other risk factors:

Breast cancer:

--American Cancer Society: Mammograms yearly beginning at age 40; breast exam by doctor at least every three years in 20s and 30s, annually after 40; breast self-exam an option.

--American College of Obstetricians and Gynecologists: Mammograms every 1-2 years for women in their 40s; annual mammograms age 50 and older; breast exam by a doctor annually from age 19; breast self-exam can be recommended.

--U.S. Preventive Services Task Force: Mammograms every two years for women ages 50 to 74, after 75 the risks and benefits unknown; recommends against self-exam; value of exams by doctors unknown.

Cervical cancer:

--Cancer Society: Start Pap tests about three years after first intercourse but no later than 21; annually or every 2-3 years for women over 30 who have three normal tests; stop at 70 after at least three negative tests and no abnormal tests in last 10 years; discontinue after a total hysterectomy.

--ACOG: Start Pap tests at age 21 and then every two years; 30 years and older, every three years after three normal tests; reasonable to stop at age 65 or 70; discontinue after hysterectomy.

--Task Force: Start Pap tests within three years of sexual activity or by age 21; at least every three years, stop after 65 if negative tests and no high risk; discontinue after hysterectomy.

Prostate cancer:

--Cancer Society: No routine testing recommended; doctors should discuss benefits and limitations, and offer screening -- a physical exam and blood test for a substance called PSA -- to men beginning at age 50, with at least a 10-year life expectancy. --Task Force: No recommendation for or against screening for men under 75; men over 75 should not be screened.

--American Urological Association: Men 40 and older should be offered a baseline PSA test and exam.

Colon cancer:

--Cancer Society and other major groups: Start screening at 50 with one of these tests: colonoscopy every 10 years; a sigmoidoscopy of the lower colon every five years; CT colonography or "virtual colonoscopy" every five years; barium enema every five years, stool blood test annually; stool DNA test, no interval given.

--Task force: Screen from age 50 to 75 with one of three tests: colonoscopy every 10 years; a sigmoidoscopy every five years, combined with a stool blood test every three years; a stool blood test every year.

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