But the study shines new doubt “over the effectiveness of an already controversial cancer screening tool that is aimed at detecting tumors before they spread and become more difficult to treat”:
Their analysis showed that, since mammograms became standard in the United States, the number of early-stage breast cancers detected has doubled — in recent years, doctors found tumors in 234 women out of 100,000. But in that same period, the rate of women diagnosed with late-stage breast cancer has dropped just eight percent — from 102 to 94 cases out of 100,000.
“We estimated that breast cancer was overdiagnosed — i.e., tumors were detected on screening that would never have led to clinical symptoms — in 1.3 million US women in the past 30 years,” authors Gilbert Welch of Dartmouth Medical School and Archie Bleyer of the Oregon Health & Science University, wrote in a study published Thursday in the New England Journal of Medicine.
“We estimated that in 2008, breast cancer was overdiagnosed in more than 70,000 women; this accounted for 31% of all breast cancers diagnosed,” they added. These women likely received major medical interventions — including surgery, radiology, hormone therapy and chemotherapy — that ought only to be used when absolutely necessary, the authors stressed.
They also concluded the significant drop in breast cancer deaths can be best explained by the improvement in treatments, rather than the early detection through mammograms.
Recent research has confirmed these findings. For instance a 2011 paper published in the Annals of Internal Medicine found that while “some women need mammograms more frequently than others,” a more complex approach to mammography “based on personal risk factors such as age, breast density, family history of breast cancer and even a woman’s personal preference” could help reduce overtreatment and unnecessary testing.
The science encourages women and doctors to consider harms of additional testing, including radiation exposure, the anxiety associated with false-positive findings on the initial examination, and the costs of additional imaging.