Breast Cancer Prevention by Mammograms Not Working, Study Shows

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Despite the increased accessibility of mammogram tests,  more breast cancer screenings did not equate to fewer deaths, according to a new study. 

The study, published in JAMA Internal Medicine, shows that although breast cancer diagnoses increased with more accessible screenings, significant number of deaths from the disease remain, and may have lead to overdiagnosis. The research also suggests that the detection of some cancers were more on small tumors instead of the more advanced or larger ones. 

"The most dramatic finding of our study is the immediately evident - and substantial - evidence of breast cancer overdiagnosis," Charles Harding, lead author of the study, told Reuters in an email. He added that the results of the study are "far from definitive."

The researchers looked at relevant information on breast cancer including screenings, diagnoses, tumors, and deaths among 16 million women in 547 counties in the United States. The scientists found that the range of mammogram screenings are from 39 percent to almost 80 percent, depending on which country.

"We were troubled that we did not see evidence of a mortality benefit from screening, especially because there was no relationship between screening and advanced-stage cancer, either," Harding said via Huffington Post.

He added that data may have been "noisy" due to several factors and limitations including ecological bias when collecting large group data.

Harding recommended further research because he believes the "study raises important questions about the benefits of mammography screening, but it certainly does not answer them."

Washington Post notes that overdiagnosis and overtreatment of cancers in general have been the subject of debate over the past few years. 

Joann G. Elmore and Ruth Etzioni, authors of "Effect of Screening Mammography on Cancer Incidence and Mortality" define overdiagnosis as the "diagnosis of a tumor that would not have become clinically apparent in the absence of screening."

The number of false positives in breast cancer mammograms can go from 10 percent to 50 percent every screening, according to Washington Post.

"Treatment of an overdiagnosed tumor cannot provide benefit, but it can lead to harm. Overdiagnosis and overtreatment are now widely acknowledged to be an important harm of medical practice, including cancer screening," Elmore and Etzioni said in the report.