What You Need to Know About Breast Cancer Screening

Mammography may find small cancers that don't affect death rate

(RxWiki News) Screening for breast cancer may be a double-edged sword.

A new study found that breast cancer screening detected more tumors that are small, slow-growing or that will shrink spontaneously. However, the study also found no change in breast cancer deaths as a result of these screenings.

“Across US counties, the data show that the extent of screening mammography is indeed associated with an increased incidence of small cancers but not with decreased incidence of larger cancers or significant differences in mortality," wrote lead study author Richard Wilson, DPhil, of Harvard University, and colleagues. "What explains the observed data? The simplest explanation is widespread overdiagnosis, which increases the incidence of small cancers without changing mortality."

The purpose of breast cancer screening is to catch cancers early so that they can be treated. Overdiagnosis occurs when breast cancer screening discovers a tumor that would otherwise not cause disease or symptoms. Treating these tumors may not be necessary and may even cause more harm than benefit, according to Dr. Wilson and team.

Director of Clinical Investigation for the University of Pittsburgh Cancer Institute, Adam M. Brufsky, MD, told dailyRx News, “Right now, [the study] changes nothing, but it is one more piece of the data suggesting that the cost of more intensive screening may be the detection of less aggressive cancers which require less aggressive treatment. It is important that we discuss this with women undergoing screening.”

Dr. Wilson and team looked at 16 million women from more than 500 counties. More than 50,000 of these women were diagnosed with breast cancer in 2000. Those diagnosed were then followed for 10 years.

As more of these women were screened, more breast cancers were diagnosed. However, the overall death rate from breast cancer remained unchanged. This suggests that overdiagnosis was occurring.

“As is the case with screening in general, the balance of benefits and harms is likely to be most favorable when screening is directed to those at high risk, provided neither too frequently nor too rarely, and sometimes followed by watchful waiting instead of immediate active treatment,” Dr. Wilson and colleagues wrote.

In a related editorial, Joann G. Elmore, MD, of the University of Washington, and Ruth Etzioni, PhD, of the Fred Hutchinson Cancer Research Center, wrote, “We need clear communication and better tools to help women make informed decisions regarding breast cancer screening mammography. Perhaps most important, we need to learn how to communicate with our patients about uncertainty and the limits of our scientific knowledge. Part of informed decision making is providing all the information, even our uncertainty."

This study was published in the July issue of the journal JAMA Internal Medicine.

Study author Francesco Pompei, PhD, is the chief of Exegen Corp. Study author Charles Harding, PhD, disclosed funding from Exegen Corp.


Review Date: 
July 2, 2015