Effect of start age of breast cancer screening mammography on the risk of false-positive results

ObjectiveTo estimate the false-positive (FP) risk according to the start age of mammography screening (45–46 or 50–51 years).MethodData from eight regions of the Spanish breast cancer screening programme from 1990 to 2006 were included (1,565,364 women). Discrete time-hazard models were used to ascertain the effect of age and time-related, programme-related and personal variables on FP leading to any further procedure and to invasive procedures (FPI). In a subset we estimated the differential FP risk of starting screening at 45–46 years (175,656 women) or 50–51 (251,275).ResultsA start age of 45–46 versus 50–51 years increased both FP (OR = 1.20; 95%CI: 1.13–1.26) and FPI risks (OR = 1.43 (95%CI: 1.18–1.73).Other factors increasing FP risk were premenopausal status (FP OR = 1.26; 95%CI: 1.23–1.29 and FPI OR = 1.22; 95%CI: 1.13–1.31), prior invasive procedures (FP OR = 1.52; 95%CI: 1.47–1.57 and FPI (OR = 2.08; 95%CI: 1.89–2.28) and family history (FP OR = 1.16; 95%CI: 1.12–1.20 and FPI OR = 1.26; 95%CI: 1.13–1.41). FP risk was increased by double reading (OR = 1.36; 95%CI: 1.23–1.51) and FPI risk by double views (OR = 1.34; 95%CI: 1.18–1.52). Both the cumulative FP and FPI risks were higher in women commencing screening at 45–46 years versus 50–51 years (33.30% versus 20.39% and 2.68% versus 1.76%).ConclusionsStarting screening earlier increases the cumulative risk of FP and FPI.

Research Highlights
► Among the harms of screening mammography are false-positive (FP) results.
► This study analyzes the effect of start age on the risk of this adverse effect.
► Starting screening mammography at 45-46 years increases this risk.
► FP results leading to invasive procedures are also higher in these women.