Mammograms aren''t a 100 percent guarantee you''re cancer free. But they''re still the best tool for detecting breast cancer early.

Doctors believe mammograms, or screening X-rays of the breast, find tumors 80 percent of the time, often years before they can be felt. But a local radiologist is worried many women aren''t getting them as regularly as they should.

Dr. Barbara Monsees is professor of radiology at Washington University and head of the breast imaging section at the Siteman Cancer Center. Monsees said she believes that some doctors may be advising women between the ages of 40 and 50 to get a mammogram every one to two years. She believes that advice puts the health of women in the younger age group at risk. She cites clinical data that shows breast cancer can grow faster and be more aggressive in women younger than 50, making annual mammograms even more important.

Annual mammograms also are recommended by several national cancer and health organizations. Both the American Cancer Society and the American College of Radiology specify healthy women over 40 should get a mammogram every year. Women considered at high risk for breast cancer may want to begin even earlier and should discuss the age of first mammogram and frequency of their breast screening with their gynecologist.

Clouding the picture, however, is a statement from the National Cancer Institute, which recommends that women over 40 get regular screening mammograms every one to two years until 50, unless considered at high risk.

According to Monsees, the NCI isn''t telling women not to get annual screenings but emphasizes medical data that supports a screening every two years until 50. She urges women to ignore the recommendation. She believes clinical studies and medical data support annual breast screenings after 40, even if the medical evidence isn''t as strong as the evidence for annual exams in women over 50.

Monsees acknowledges that mammograms are far from fool-proof, so she also advocates annual clinical exams by a physician and urges women to practice monthly breast self-exam. But she insists that mammograms remain the best tool medicine has for detecting many breast tumors.

Kay Quinn is an anchor and reporter for KSDK (Channel 5).