Study shows low rates of breast cancer overdiagnosis in mammography

UK: Results from a case-control study in Cancer Medicine have revealed that mammography benefits outweigh overdiagnosis risks, especially since the rate of overdiagnosis is low. 

Considering the uncertainty about overdiagnosis in mammography screening, Stephen W. Duffy, Queen Mary University of London, London, UK, and colleagues aimed to estimate the effect of screening on breast cancer incidence and overdiagnosis in the NHS Breast Screening Programme in England.

57,493 cases and 105,653 controls were included in the study, with cases defined as women diagnosed at ages 47–89 with primary breast cancer, invasive or ductal carcinoma in situ, in 2010 or 2011. Where possible two controls matched on date of birth and screening area were selected per case. 

To estimate the effect of screening on breast cancer risk, conditional logistic regression was used. To estimate absolute rates of overdiagnosis, results were combined with national incidence data. Calculation of overdiagnosis was done as the cumulative excess of cancers diagnosed in the age group 50–77 in a woman attending three-yearly screening between ages 50 and 70 compared with a woman attending no screens.