The Positive and Negative Results of Cancer Screenings

Read about the study that launched the controversial new guidelines for breast cancer screening. 

Oct. 20, 2009. In the past 20 years, since screening for breast and prostate cancer has become routine, detection and treatment has skyrocketed. That's a good thing, right? Not necessarily, say the authors of an opinion piece published this week in the Journal of the American Medical Association (JAMA).

After two decades of screening, the overall rates for both cancers has almost doubled, many more patients are being treated, but the incidence of aggressive or later-stage disease has not been significantly decreased, the conclude the authors, researchers from the University of California, San Francisco and the University of Texas Health Science Center at San Antonio.

Each year breast cancer--the most common form in women--strikes 200,000 American women and accounts for 40,000 deaths. For men, prostate cancer gets the number one spot. This year, an estimated 192,280 US men will be diagnosed and 27,360 men will die from it.

"Screening does provide some benefit, says co-author Laura Esserman, MD, MBA, professor of surgery and radiology at  UCSF. But she adds, "The problem is that the benefit is not nearly as much as we hoped and comes at the cost of over-diagnosis and over-treatment."

While deaths have dropped for both cancers over the last 20 years, it's not clear how much can be attributed to screening. For instance, a comparison of prostate cancer incidence rates in the US and the United Kingdom, where PSA screening has not been widely adopted, “did not result in significant differences in mortality,” they write. The relative reduction in deaths from screening for breast cancer has also been limited and  because screening increases the detection of slow growing and "idle" tumors, many patients are undergoing treatment from cancers that actually pose minimal risk.

“The basic assumption that screening programs that find and treat early stage disease will then prevent late-stage disease, or prevent cancer from spreading, may not always be correct,” says co-author Ian Thompson, MD, who holds a Chair in Genitourinary Oncology at the Cancer Therapy & Research Center and is the chairman of the Department of Urology at the Health Center at UT San Antonio. “If a tumor is aggressive, finding it early may not prevent death.” In contrast to breast and prostate cancer, screening for cervical and colon cancer—and the removal of abnormal tissue – has led to a significant drop in invasive cancer.