(This story has been updated with a correction on Feb. 19, 2014.)
The increasingly contentious debate over the role of screenings in the early detection of breast cancer grew a little more contentious with the release Tuesday in the BMJ
of a study that contends that annual mammography in women ages 40 to 59 does not reduce death from breast cancer.
Researchers in Canada followed 89,835 women for 25 years, comparing the incidence and mortality for women diagnosed with breast cancer
who had received routine mammograms versus those who had not. A total of 1,190 breast cancers were diagnosed: 666 in women who had mammograms and 524 in the control group. But after 25 years, nearly the same amount of women in each group had died from the disease. The study found that 22% of invasive breast cancers detected by screening were overdiagnosed, meaning that the women were exposed to unnecessary procedures for cancers that were slow-growing or did not require treatment.
“In technically advanced countries, our results support the views of some commentators that the rationale for screening by mammography should be urgently reassessed by policymakers,” the study authors concluded.
The results are the latest to add to the back-and-forth over the effectiveness and safety of breast cancer screening. Imaging and radiology groups were among the first to respond, offering harsh criticism of the findings.
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 in a news release
. The groups argued that the low number of breast cancers detected in the study is the result of “poor quality mammography,” and that using this study to create breast cancer screening policy would place women at increased risk of dying unnecessarily from breast cancer.
But others warn too much screening can be a bad thing, and that this study offers important insight that can help protect patients from unnecessary harm.
“One of the real challenges in medicine is to recognize that the things we believe may or may not be true,” said Dr. Virginia Moyer, chair of the U.S. Preventive Services Task Force. This is a very important study, she says, one the USPSTF will take into consideration as it revisits its guidelines over the next year and a half. “Every mammogram does not save a life. Mammography is a tool, it does not work particularly well and this paper suggests that it may not work at all,” she said.
In November 2009, the USPSTF received backlash when it issued recommendations that many interpreted as advising against giving routine mammograms to women in their 40s. The task force later issued a clarification, explaining that biennial screening mammography before age 50 should be an individual decision between the patient and her doctor, in which the specific benefits and harms would be clearly communicated. “The task force did not say don't do mammograms because the data we looked at showed a modest benefit. This study challenges even that,” Moyer says.
“We agree,” Dr. Judith Salerno, president and CEO of Susan G. Komen
wrote in response to the BMJ study. “We need tests that can tell us, with more certainty, which tumors are likely to become invasive and which might not require extensive treatment.” Screening tools for breast cancer are based on 1950s technology, she said, and can lead in some cases to over-diagnosis and overtreatment.
As the debate over the mammography continues, advocates say early detection remains a vital tool in saving lives from breast cancer. According to the American Cancer Society, 60% of breast cancers are diagnosed at a localized stage, for which the five-year survival rate is 98%. Inadequate screening is associated with more advanced tumor size and stage at diagnosis. ACS recommends
yearly mammograms starting at age 40 and continuing for as long as a woman is in good health.
For now, Moyer said physicians should continue to follow existing recommendations, but should be prepared for possible changes.
“The usefulness of screening goes down as your ability to prevent a problem goes up. We're doing a better job at preventing breast cancer,” she said. “We will be reviewing this study and any other future information as we revise our recommendations. This appears to be a strong study and it will be taken into account.”(This article has been updated to correct the figures regarding the number of women who were overdiagnosed.)Follow Sabriya Rice on Twitter: @MHsrice