The researchers estimated that among 10,000 women in their 40s who undergo annual mammography for 10 years, about 190 will be diagnosed with breast cancer. Of those 190, the researchers estimate that about 5 will avoid death from breast cancer due to screening. About 25 of the 190 would die of breast cancer regardless of whether they have a mammogram or not. The rest will survive, thanks largely to advances in breast cancer treatment.
However, according to Keating, the chief harm associated with mammography is the risk of overdiagnosis. This is the diagnosis of cancers that never would have become clinically evident during a woman's lifetime, either because the cancer never grew or because the patient died first of another cause. While it is impossible with current techniques to know which cancers we could safely observe and which need to be treated, the review cites findings that roughly 19 percent of women who are diagnosed based on findings from a mammogram are overdiagnosed. That means that roughly 36 of the 190 women who received annual mammography for 10 years and were diagnosed with breast cancer would receive unnecessary surgery, chemotherapy or radiotherapy.
In addition, more than half of women who get annual screenings for 10 years can expect to have a false positive mammogram that requires additional images, and about 20 percent of these false positives result in unnecessary biopsies. Studies show these false positives cause some short-term anxiety, but there is not consensus about lasting harm.
"While we need more research on mammography's benefits and harms today, exi
|Contact: David Cameron|
Harvard Medical School