October 25, 2011 — About 25% of breast cancer survivors avoided death because they had a mammogram, while 75% would have had the same outcome if they detected the lump themselves or received no treatment, according to a study released Monday in the Archives of Internal Medicine, the Los Angeles Times' "Booster Shots" reports (Kaplan, "Booster Shots," Los Angeles Times, 10/24).
For the study, Dartmouth researchers Gilbert Welch and Brittney Frankel used National Cancer Institute software to estimate the 10-year risk of diagnoses with invasive breast cancer or ductal carcinoma in situ and 20-year risk of death for women of various ages (Phend, MedPage Today, 10/24). They also accounted for the benefits of early detection and improved treatments. They concluded that among the 60% of women with breast cancer who were diagnosed through screening mammograms, 3% to 13% of them were helped by the test.
The findings translate to 4,000 to 18,000 women who benefit from screening mammography each year, representing a small portion of the 230,000 women diagnosed with breast cancer annually and an even smaller fraction of the 39 million women who undergo mammograms annually.
"The presumption often is that anyone who has had cancer detected has survived because of the test, but that's not true," Welch said, adding that breast cancer survivors diagnosed after a mammogram are "more likely to have been overdiagnosed than actually helped by the test" (Parker-Pope, "Well," New York Times, 10/24).
"Booster Shots" notes that as the number of women who have been screened has increased in recent decades, the portion whose lives were saved by mammograms has shrunk.
"This self-reinforcing cycle … is driven, in part, by the presumption that every screen-detected breast cancer survivor has had her 'life saved' because of screening," Welch and Frankel write in the study. They add, "Our analyses suggest this is an exaggeration. In fact, a woman with screen-detected breast cancer is considerably more likely not to have benefited from screening. We believe that this information is important to put cancer survivor stories in their proper context" ("Booster Shots," Los Angeles Times, 10/24).