More than a million US women have received unnecessary and invasive cancer treatments over the last 30 years, thanks to routine mammograms that detected harmless tumors, scientists said Thursday.
The results throw 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.
To reach the one million figure, researchers compared the number of breast cancer cases detected at early and late stages among women over 40 between 1976 and 2008.
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.