Overdiagnosis of ductal carcinoma in situ: ‘the pathology equivalent of racial profiling’

Danish researchers are providing new evidence that many breast cancers found via screening mammograms don’t need to be treated. Women with these non-threatening tumors are said to be “overdiagnosed” with breast cancer.

Overdiagnosis occurs when breast screening such as mammography detects small, slow-growing cancers that may never cause the patient any trouble. Yet, women diagnosed with such tumors are exposed to very real harms–possible surgery, chemotherapy, radiation, and living life as a “cancer patient.”

How much overdiagnosis are we talking about?

If you don’t include cases of ductal carcinoma in situ (DCIS) in the tallies, anywhere from 14.7% to 38.6% of breast cancers found via screening represent overdiagnosis, the study authors found. The rate ranges from 24.4% to as high as 48.3% when DCIS is included.

DCIS is a collection of abnormal cells inside a milk duct that may–but usually doesn’t–break out to become invasive and potentially lethal cancer. About 60,000 women are told they have DCIS each year in the United States. Some experts estimate that up to 80% of women with DCIS found via screening may not need any treatment at all–and instead should just keep an eye on things.

Obviously, women need to be fully and accurately informed about the benefits and risks — including the risk of overdiagnosis — before embarking on any decision to get screened for breast cancer or choosing a course of action following a diagnosis.

Otis Brawley, MD, Chief Medical Officer for the American Cancer Society, says it’s been difficult for modern medicine to wrap its brain around the concept of overdiagnosis. The natural inclination is to assume that cancerous-looking cells “will grow, spread, and eventually kill,” he writes in an editorial accompanying the Danish study. “However, some of these lesions may be genomically predetermined to grow no further and may even regress. In many respects, considering all small breast lesions to be deadly and aggressive types of cancer is the pathologic equivalent of racial profiling.”

This doesn’t mean that screening is worthless and should be abandoned, he says. “Instead, we must carefully examine screening, realize its limitations, maximize its effectiveness, and try to improve it.”

That editorial is well worth reading in its entirety. But if you don’t have access, or if you want to hear more from the ACS’s top medical official on the theme of “pathologic profiling” — as well as a variety of other timely issues in medicine and health journalism — then I recommend a listen to our 2015 podcast featuring Brawley.

Publisher Gary Schwitzer connected with him at the 2015 Preventing Overdiagnosis in Washington.

Other resources:

Our podcast with Dr. Laura Esserman, a surgeon and breast cancer specialist who’s thought and written extensively about DCIS and overdiagnosis.

Our podcast with Dr. Saurabh Jha, a radiologist who says his profession can be both the arsonist and firefighter when it comes to overdiagnosis.

Our podcast with Dr. John S. Yudkin, an emeritus professor of medicine at University College in London, who spoke about overdiagnosis of diabetes.

 

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