Are Mammograms Overdiagnosed?

When to do -- or not do -- a mammogram; that is the question. How frequently and at what age women should begin to get mammograms isn't set in stone. Guidelines vary. For example, the American Cancer Society recommends annual mammograms for all women starting at age 45 (then every other year at age 55), whereas the U.S. Preventive Service Task Force recommends mammograms for most women every two years starting at age 50.

Now, a study from the Harvard School of Public Health adds fuel to the debate by stating that routine mammograms may lead to significant overdiagnosis of breast cancer, causing undue anxiety, additional costly testing, and unnecessary breast cancer treatment.

The researchers analyzed data from a study of almost 40,000 Norwegian women with invasive breast cancer, 7,793 of whom were diagnosed during a 10-year rollout of the Norwegian Breast Cancer Screening starting in 1996. Researchers expected to see a decrease in late-stage breast cancer cases, thanks to mammography detecting early-stage breast cancer. The researchers didn't find a decrease in late-stage breast cancer cases, but they did find considerable overdiagnosis, as reported in the Annals of Internal Medicine. Of the 7,793 women who chose to be screened, 15% to 25% were overdiagnosed.

Part of the issue, the researchers say, is that radiologists have been trained to find the tiniest tumors, including those that might never blossom into breast cancer to cause symptoms or death.

The fact is, overdiagnosis of breast cancer is inevitable, given the difficulty in distinguishing between tumors that can escape the breast, spread throughout your body and kill you, and slow-growing tumors that never leave the breast and aren't life-threatening. 

"The situation is very similar to prostate cancer screening, and even lung cancer screening, where some people are going to be treated unnecessarily, but some are going to be helped," says RealAge Chief Medical Officer Keith Roach, MD. "Because we can't tell, we doctors universally recommend aggressive treatment."

Moreover, the Harvard study "doesn't address or even question the fact that mammographic screening saves lives," Roach says. "This is the most important take-home message. I'll continue to recommend mammograms for women ages 50 to 74, and discuss the issue with younger and older women."

He notes that a landmark trial found "most of the cancer deaths in the screened group were 'interval' cancers -- not there the previous screening and too late to do anything about when caught. That is, unfortunately, the peril of screening: The most aggressive cancers are likely not to be caught, while the ones you do catch are slow-growing, even the ones destined to never bother you at all -- hence, overdiagnosis."

Should women get screened and risk overdiagnosis, or skip screening and risk missing a life-threatening cancer? Ultimately, it's up to you and your doctor to decide when to start breast cancer screenings, based on your family history and comfort level, and how frequently to get them.

Take this assessment to check your risk of breast cancer.

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