Canadian study casts more doubt on mammograms

The already contentious debate over breast cancer screening heated up last week when new research showed annual mammograms for women under 60 failed to reduce deaths from the disease. The study gave new ammunition to critics who say the false positives from widespread screening unnecessarily run up healthcare spending.

The Canadian study, which was published in the journal BMJ, followed nearly 90,000 women for 25 years, half of whom had routine mammograms, half of whom didn't. Deaths from cancer were nearly identical in the two groups, even though 666 screened women were diagnosed with cancer compared with 524 in the control group. One out of every 424 women who received screening was overdiagnosed, the study stated. “The rationale for screening by mammography should be urgently reassessed by policymakers,” the study authors wrote.

That statement drew immediate fire from radiologists. The report is “an incredibly misleading analysis based on the deeply flawed and widely discredited Canadian National Breast Screening Study,” the American College of Radiology and Society of Breast Imaging responded. The group suggested that the low number of breast cancers reported in the study resulted from “poor quality mammography” associated with older technologies.

This latest study now goes before the U.S. Preventive Services Task Force, which is re-evaluating its guidelines on breast cancer screening. Its 2009 recommendations, which advised women under 50 to avoid mammography, triggered a national uproar. The government-appointed group subsequently clarified its guidelines to state that screening should take place only after women consulted with their doctors and had the benefits and risks of overdiagnosis carefully explained.

“This study challenges even that,” said Dr. Virginia Moyer, chair of the USPSTF. The group's recommendations determine what preventive services must be delivered free of charge in policies sold on the new health insurance exchanges.

Even some of the strongest proponents of widespread screening said the latest study offers proof that mammography, a test developed in the 1950s, is outdated. “We need tests that can tell us, with more certainty, which tumors are likely to become invasive and which might not require extensive treatment,” said Dr. Judith Salerno, president and CEO of Susan G. Komen.

Follow Sabriya Rice on Twitter: @MHsrice