Is Mammography Harming More Women Than It Saves?

Breast cancer screening harms outweigh benefits study suggests

(RxWiki News) A new study looking at 30 years of screening mammography suggests that we are over-diagnosing breast cancer by about one third – 31 percent. A nationally known breast cancer screening expert and advocate responds to the study by saying, “Enough is enough.”

That means, according to these researchers, that 1.3 million breast cancers diagnosed between 1976-2006 were early disease that didn’t need to be treated.

The study suggests that screening mammography is detecting too many young breast cancers that likely would not have caused the individual a problem, while causing substantial harm by over-treating harmless tumors.

"Talk to your doctor about breast cancer screening."

Archie Bleyer, MD, medical advisor to the St. Charles Regional Cancer Center and H. Gilbert Welch, MD, MPH, professor of medicine and community and family medicine at Dartmouth Medical School, conducted the review.

They charted when in the disease process that the breast cancer diagnosis was made. The benefit of any screening is to find cancer in its earliest and most treatable stage with the primary objective being to prevent cancer deaths.

“Our study raises serious questions about the value of screening mammography. It clarifies that the benefit of mortality reduction is probably smaller, and the harm of overdiagnosis probably larger, than has been previously recognized,” the authors wrote.

Daniel B. Kopans, MD, professor of radiology at Harvard Medical School and senior radiologist - the Breast Imaging Division - Massachusetts General Hospital, couldn’t disagree more.

“It is time to stop blaming mammography screening for ‘overdiagnosis’ and ‘overtreatment’ in an effort to deny women access to screening,” Dr. Kopans told dailyRx news. “Every major group, including the United States Preventive Services Task Force and the American College of Physicians that has looked at mammography screening agrees that it reduces deaths for women who begin screening at the age of 40.”

For this study, the researchers looked at how many breast cancers were diagnosed between 1976 through 1978 without the use of mammography. Those numbers were then tracked over the years and compared to the number of diagnoses resulting from mammography between 2006-2008.

They used Surveillance, Epidemiology, and End Results data to look at both early-stage breast cancers, including ductal carcinoma in situ (disease that is not invasive) and late-stage disease that has spread in women ages 40 and older.

Since its introduction, screening mammography has more than doubled the number of early-stage cancers diagnosed in this country –from 112 to 234 cases per 100,000 women. Meanwhile, the diagnosis of late-stage cancers has decreased by 8 percent.

According to researchers’ calculations, “only 8 of the 122 additional early-stage cancers diagnosed were expected to progress to advanced disease.”

So the authors are suggesting that the benefits of mammography are modest, while the potential harms of unnecessary treatment - surgery, chemotherapy, radiation and years of hormonal therapy - are substantial.

“Mammography does not cause ‘overdiagnosis,’” Dr. Kopans said: “Unfortunately, pathologists are not yet able to distinguish cancers that will be lethal if left untreated from those that do not need treatment.”

“Unfortunately, approximately 40,000 women still die each year from breast cancer. Would opponents of screening argue to stop all treatment since so few actually benefit?”

“Enough is enough,” Dr. Kopans said. “There is a small group of highly vocal individuals who have decided that they wish to end all screening for breast cancer. All responsible groups agree that mammography screening saves lives.”

Instead, his report said, “Women should recognize that our study does not answer the question ‘Should I be screened for breast cancer?’ However, they can rest assured that the question has more than one right answer.”

This study was published November 21 in the New England Journal of Medicine. Dr. Bleyer disclosed he is a consultant with Sigma-Tau Pharmaceuticals on acute lymphoblastic leukemia, and Dr. Welch provides analytic services to MedPAC (Medicare).

Review Date: 
November 21, 2012