Mammograms: Huge Impact Seen on Reducing Cancer Deaths
April 23, 2001 (Dana Point, Calif.) -- Message to women: regular mammograms are worth it. That's according to a major new study from the American Cancer Society.
A first look at the study -- scheduled for publication in the May 1 issue of the journal Cancer -- shows that women who get regular mammograms have 63% fewer deaths from breast cancer than women who don't. This is far better than earlier estimates from clinical trials. The results were presented here Monday at the society's Science Writers Seminar.
"We have a truer estimate of the benefit -- roughly twice the one that is usually communicated," says Robert A. Smith, PhD. "This benefit is likely to be even better with annual screening -- because this data is based on screening every 24 months."
Smith, director of cancer screening for the American Cancer Society, and his co-workers analyzed detailed medical records from two counties in Sweden. They compared breast cancer deaths from 1988 to 1996 among women who actually got regular mammograms to breast cancer deaths from 1968 to 1977, before mammograms became available.
Earlier clinical trials set up to prove that mammograms worked had to compare women who were supposed to get the tests to women who were not supposed to get the tests. These important studies proved their point -- that mammograms work to prevent cancer deaths -- but they underestimated their effect. Smith says this is because some women who were supposed to get mammograms did not show up for their exams, and some women who were not supposed to get mammograms went to doctors outside the trial to get them.
"These results should provide an incentive to find strategies to increase screening participation rates," Smith says.
The study strongly suggests that early detection of breast cancer was more important in preventing cancer death than new treatments for the disease. Smith estimates that 70% of the reduction in cancer deaths seen in Sweden were due to catching the disease in its earliest stage -- when there is a 95% cure rate.
"The last 20 years have resulted in considerable improvement in prognosis attributable to improvements in treatment, in women's awareness, and to detection," Smith says. "To argue which does the most is unproductive. But in terms of overall potential to improve mortality, the most significant factor is finding tumors when they still are very small."
"This study shows us that when breast cancer [screening] is made available -- and when women are faithful in doing it -- the benefits may be even greater than those reported in clinical trials," says breast cancer expert Marilyn Leitch, MD, professor of surgery at the University of Texas Southwestern Medical Center in Dallas.