New research on mammography suggests the benefits of this routine test don't actually outweigh the risks for many women.

That means a woman's decision to have mammography should be individualized, researchers said.

Report co-author Dr. Nancy Keating, an associate professor of Health Care Policy at Harvard Medical School, said their analysis indicates mammography guidelines should be based on each individual patient's complete health profile, such as family and medical history, genetic risk factors and overall life expectancy. Researchers studied 50 years of breast cancer research.

"Mammography does have some benefit in the likelihood of dying from breast cancer, but these benefits are relatively modest," Keating told CBS News. "Particularly for women who are at very low risk of breast cancer -- the benefits are quite small."

The authors found mammography reduces breast cancer mortality rates overall by about 19 percent. For women in their 40s, regular screening with mammography only lowered breast cancer-related deaths by around 15 percent. Post-menopausal women were found to benefit the most from annual mammography; the screening test lowered death rates of women in their 60s by 32 percent.

Overall U.S. women have a 12.3 percent lifetime risk for developing the breast cancer. About 40,000 women will die from the disease this year, according to the American Cancer Society.

Mammography is the most common screening test for breast cancer but it's not always accurate. Statistically, mammography misses about 20 percent of breast cancer malignancies, according to the National Cancer Institute. On the other hand, the test can also lead to false positive results, over-diagnosis and even unnecessary treatment.

By the authors' calculations, more than half of the women who have routine mammography over 10 years can expect a false positive diagnosis, and 20 percent of these false positives will lead to unnecessary biopsies.

Another controversial study, published in February by the British Medical Journal, tracked 90,000 women who had routine mammograms over a period of 25 years. That study also found regular mammograms didn't necessarily lower risk for breast cancer death, even for women in their 50s, when the risk for developing the disease typically starts to increase.

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