New mammography guidelines: Should we apply them to our Black patients?

black_mammoWe’re currently in a heated debate about the pros and cons of conducting breast cancer screening with mammography in women aged 40 to 49. This debate is raging in the wake of the United States Preventive Services Task Force (USPSTF) announcement of new guidelines on mammography. The USPSTF does not recommend such screening in women less than 50 years old without their informed consent with respect to the potential harm of such screening.

Some African-American organizations, such as the National Medical Association, have come out in favor of continuing to recommend mammography for African-American women 40-49 years old. They argue that because African-American women are at higher risk of dying from the disease, it’s appropriate to do massive screening of the population.

This past spring, I wrote a blog post on the detrimental effects of prostate cancer screening, and what I said then is relevant to the current debate on breast cancer screening. After discussing recent studies that show the harm caused by broad prostate cancer screening, I took up the argument that — because African Americans suffer more disproportionately from the disease — screening is appropriate in that population. “However,” I said, “some would argue that the situation is different for African-American men. The burden of this disease does not fall evenly across the population. African Americans get it more often. African Americans get it at a younger age. African Americans die from the disease in disproportionately high numbers. The problem for African-American men, this argument goes, is not overdiagnosis and overtreatment of prostate cancer, but rather its underdiagnosis and undertreatment.”

“That’s a straw-dog argument. It really highlights the fact that African Americans have poor access to health care; however, it doesn’t assess the effect of screening on African-American men. If you look at the United States, out of 100 men, 20 will develop prostate cancer in their lifetime. Of that 20, three will die from their prostate cancer. Among African-American men, five of 20 will die from their prostate cancer. Although we can’t tell our patient with prostate cancer sitting in the exam room in front of us whether he will die from the disease, it’s clear that most men with prostate cancer won’t die from it. PSA testing, therefore, leads to finding and treating clinically insignificant cancers — for both whites and African Americans.”

Overdiagnosis is not just limited to prostate cancer in men. Mammography detects breast cancer in women who would otherwise have lived their lives never knowing that they had breast cancer.

Overdiagnosis is a different problem than getting falsely positive results. As noted by the USPSTF, nearly 2,000 women need to be regularly screened over the course of 10 years to prevent one woman from dying from breast cancer. However, during that same period, 10 healthy women will be falsely identified as breast cancer patients and treated unnecessarily. These women are harmed by a false-positive mammography.

With overdiagnosis, patients are correctly told they have breast cancer and are subsequently treated; however, if they hadn’t had the mammography, they would have lived the rest of their lives unaware that they ever had breast cancer. One third of women between the ages of 40 years and 54 years who die from other causes have breast cancer found on autopsy. In countries with massive breast cancer screening programs, approximately 1 in 3 women will be diagnosed with breast cancer that, had they not been screened, would not have affected them.1

What does it mean to say that overdiagnosis of breast cancer occurs 1 in 3 women? For every 1000 women over 50 screened for breast cancer with annual mammograms for 10 years: 1 woman will avoid dying from breast cancer; 2 to 10 women will be overdiagnosed and unnecessarily treated; 10 to 15 women will find out they have breast cancer but it won’t affect their disease course; and 100 to 500 women will have at least one false-positive finding, with about half of these women receiving biopsies.

As with prostate cancer screening in men, the most prudent thing for clinicians to do is to help our female patients make an informed medical choice regarding breast cancer screening. We should give them the facts regarding the modest benefit of breast cancer screening today versus the harm of overdiagnosis and overtreatment of this disease and let our patients make the choice to be screened or not. This approach is as true for African-American women as it is for others.

1. Welch HG. Overdiagnosis and mammography screening. BMJ 2009;339:b1425)

Monday, November 23rd, 2009 at 05:29