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Time to rethink the way cancer screening is promoted
Source: (cancerfacts.com)
Tuesday, October 27, 2009
SAN FRANCISCO – Oct. 27, 2009 – Is detecting breast and prostate cancers at their earliest stages paying off in reductions in later stage cancers and of dying of the two diseases? A new study says no, touching off a new round of controversy over the strategy of screening for very early stage cancers.
Led by Dr. Laura Esserman at the University of California at San Francisco and Dr. Ian Thompson of the University of Texas, an analysis of the past 20 years of screening for breast and prostate cancer showed that, while detection of early stage disease nearly doubled for both cancers, there was not a corresponding reduction in regional disease as would be expected if early detection were resulting more cases being cured at the early stage.
"One possible explanation is that screening may be increasing the burden of low-risk cancers without significantly reducing the burden of more aggressively growing cancers and therefore not resulting in the anticipated reduction in cancer mortality," the authors wrote.
The study results were published in the current issue of the Journal of the American Medical Association, and have re-ignited the controversy about the value of screening. The American Cancer Society has been quick to reassure people that while they conduct ongoing review of the research and make changes to their guidelines, they are not changing their guidelines in light of this latest study just yet.
In a statement issued in response to the New York Times Oct. 21 story about this latest study, Dr. William Brawley, chief medical officer for the ACS, wrote that the findings suggest that current screening methods are not perfect.
"While the advantages of screening for some cancers have been overstated, there are advantages, especially in the case of breast, colon and cervical cancers. Mammography is effective – mammograms work and women should continue get them," Brawley wrote. "Seven clinical trials tell us that screening with mammography and clinical breast exam do reduce risk of breast cancer death. This test is beneficial in that it saves lives, but it is not perfect. It can miss cancers that need treatment, and in some cases finds disease that does not need treatment."
The Society's guidelines regarding screening for prostate cancer already are more moderate, reflecting the relatively lower precision of the prostate specific antigen (PSA) test and the very nature of prostate cancer.
"Since 1997 the American Cancer Society has recommended that men talk to their doctor and make an informed decision about whether or not prostate cancer early detection testing is right for them. This recommendation also still stands," Brawley adds.
Experts in both diseases have long acknowledged that aggressive cancer screening does pose the risk of over diagnosis and overtreatment. Current estimates suggest that for every 100 women who are told they have breast cancer, as many as 30 have tumors that are so slow-growing they are unlikely to be life-threatening. Similarly in the case of prostate cancer, for every 100 men diagnosed, as many as 70 have cancers that likely would never pose a threat to them.
The bottom line seems to be that screening should continue to be done, but patients need to understand that current screening methods are not certain. Meanwhile researchers need to develop better screening methods to allow patients and doctors to more accurately assess the real risk posed by a given diagnosis. As Esserman's research team concluded, better methods should help avoid treating cancers that don't need to be treated and reduce deaths from those that do.
"To reduce morbidity and mortality from prostate cancer and breast cancer, new approaches for screening, early detection, and prevention for both diseases should be considered," they wrote.
SOURCE: JAMA 2009;302(15):1685-1692. Rethinking Screening for Breast Cancer and Prostate Cancer Laura Esserman; Yiwey Shieh; Ian Thompson. http://jama.ama-assn.org/cgi/content/full/302/15/1685
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