Catching cancer early in a mammogram can be life-saving — smaller tumors are easier to remove surgically, and therapy often has a much greater effect. But paradoxically, breast cancer screening also sometimes picks up tumors that would have caused less harm if they’d remained hidden.
These cases, known as “overdiagnoses,” may never go on to pose a threat to a patient’s health for a number of different reasons. A new study, published Monday in Annals of Internal Medicine, suggests they occur in 1 of 7 breast cancer cases detected during screening. That new estimate comes as a relief to breast cancer clinicians, who say that the study should reinforce the idea that the benefits of mammography generally outweigh its risks. Still, experts said, it doesn’t minimize the real danger of overdiagnosis or the need to effectively communicate the risks and benefits of screening to patients.