BREAST ENLARGEMENT AND REDUCTION - RESULTS FROM A BREAST-CANCER CASE-CONTROL STUDY

In a population-based case-control study of breast cancer that include d 2174 cases and 2009 population controls under 55 years of age, prior breast implants were reported by 36 cases Versus 44 controls. After a djustment for the matching factors as well as variables associated wit h both breast cancer risk and breast enlargement (race, family history of breast cancer, body size, screening history), the relative risk of breast cancer associated with a prior implant was 0.6 (95% CI 0.4-1.0 ). The reduced risk persisted with increasing interval since surgery, arguing against selection bias as an explanation. Further, although a deficit of in situ tumors was seen among women with implants (RR = 0.2 ), the risk associated with implants remained reduced for both localiz ed and distant tumors (RR = 0.8 for both stages). In a smaller group o f women who had prior breast reduction surgery (10 cases, 13 controls) , a reduced risk of breast cancer also was observed (RR = 0.7, 95% CI 0.3-1.6). The results of this study must be interpreted cautiously bec ause of the small number of women involved and reliance on patient rep orts of prior operations. In not showing any elevation in breast cance r risk following a breast implant, our results confirm several record linkage studies but contradict some clinical studies that suggest an a dverse effect. Additional investigations are needed in relation to spe cific types of breast implants, including the polyurethane-coated impl ants, which have been linked to high cancer rates in laboratory animal s.