Posted 10/22/2009 1:54 PM (GMT 0)
American Cancer Society changes course on screening
quoted below:
http://www.nytimes.com/2009/10/22/he....html?_r=1&hpw
related article, with graph:
http://www.nytimes.com/2009/10/21/he...cancer.html?em
Benefits and Risks of Cancer Screening Are Not Always Clear, Experts Say
By TARA PARKER-POPE
Published: October 21, 2009
Most people believe that finding cancer early is a certain way to save lives. But the reality of cancer screening is far more complicated.
Studies suggest that some patients are enduring aggressive treatments for cancers that could have gone undetected for a lifetime without hurting them. At the same time, some cancers found through screening and treated in the earliest stages still end up being deadly.
As a result, the chief medical officer for the American Cancer Society now says that the benefits of early detection are often overstated. The cancer society says it will continue to revise its public messages about cancer screening as new information becomes available.
While the limits of cancer screening have long been known in the prevention community, the debate is new and confusing to many patients who have been told repeatedly to undergo screening mammograms or annual blood tests to gauge prostate cancer risk.
“The health professions have played a role in oversimplifying and creating the stage for confusion,” said Dr. Barnett S. Kramer, associate director for disease prevention at the National Institutes of Health. “It’s important to be clear to the public about what we know and be honest about what we don’t know.”
Nobody is suggesting that women stop getting mammograms or that men stop discussing prostate cancer screening with their doctor. Instead, the goal is to update public health messages to better reflect the benefits, risks and limits of various forms of cancer screening, Dr. Otis Brawley, chief medical officer of the American Cancer Society, said in an interview.
In a news release issued Wednesday, the cancer society affirmed its current guidelines recommending annual mammography screening for women ages 40 and older, and the group advises men to discuss the risks and benefits of prostate cancer screening with their doctors. But understanding the limitations of screening, the statement said, will help researchers develop better screening tests.
“Cancer is a complicated disease,” Dr. Brawley said. “We shouldn’t try to fight it with simplistic messages.”
Overdiagnosis and overtreatment as a result of cancer screening are a major concern. It is estimated that for every 100 women who are told they have breast cancer, as many as 30 have cancers that are so slow-growing they are unlikely to be life-threatening.
In the case of prostate cancer, for every 100 men with diagnoses, as many as 70 have cancers that if left untreated would never have harmed them. Even for men with aggressive prostate cancer, whether screening improves the odds of survival remains a matter of debate.
“It’s not that screening doesn’t do any good,” said Dr. Laura J. Esserman, a professor of surgery and radiology at the University of California, San Francisco, and co-author of a new analysis of screening risks and benefits in The Journal of the American Medical Association. “But it’s not the answer for every kind of cancer, and it’s not going to fix all the problems.”
“If you get screened, there’s a chance you’re going to find a cancer that might not be dangerous, and you want to make sure you understand that so you don’t get overtreated,” Dr. Esserman added.
One goal of the screening community is to communicate cancer statistics better. It is a commonly cited fact that mammography screening for breast cancer lowers a woman’s risk of dying from the disease by 20 percent, compared with women who do not get screened. That sounds like a big benefit, but it does not fully communicate the extent to which an individual woman is helped by screening.
Another way to describe the benefits of mammography screening is this: You would have to screen 1,000 women ages 50 and older for 10 years in order to avert one additional death from breast cancer, compared to a similar number of women who are not screened.
For men screening for prostate cancer, the data are less clear. An American study showed no statistical difference in prostate cancer death rates among men who were screened, compared with men who were not. A European study showed that screening reduced the risk of dying from prostate cancer by about 20 percent. But in terms of individual risk, that is not a huge benefit. It means that a man who is not screened has about a 3 percent average risk of dying from prostate cancer. If that man undergoes annual screenings, his risk drops to about 2.4 percent.
Some doctors are worried that restating the public health message about mammography, in particular, will just confuse patients. “We don’t want to abandon what we have now or confuse people,” said Dr. Marisa Weiss, a breast oncologist and founder of the Web site BreastCancer.org.
Many patients do not understand why screening for cancer might be risky. But for every 1,000 healthy women who undergo annual mammograms, about half will have a stressful false positive within 10 years, and 180 of them will undergo a biopsy.
For men undergoing prostate cancer screening, the downside is even greater. Most prostate cancers occur in older men and are so slow-growing that the patient would die from something else before the cancer became a problem. Yet about 30,000 men do die each year of the disease.
It is impossible to distinguish between harmless prostate cancers and deadly ones. As a result, many of the 200,000 men who receive prostate cancer diagnoses annually are subjected to aggressive treatments that render them incontinent and impotent.
“Patients often are not aware that there are risks associated with cancer screening,” said Dr. Therese Bevers, medical director of the cancer prevention center at University of Texas M. D. Anderson Cancer Center. “We need to have more conversations with our patients about that.”