REDUCED BREAST-CANCER RISK AFTER REMARRIAGE - EVIDENCE OF GENETIC IMMUNE PROTECTION

Several reproductive factors have been found to be associated with bre ast cancer. Based on an immunologic rather than strictly hormonal inte rpretation of these observations, we hypothesised that, beyond the obs erved associations relating to pregnancy per se, multiple marriages wo uld be found to protect women against breast cancer. We obtained cases and controls from linked records from the Utah Cancer Registry and ge nealogic records. A total of 2,414 women with newly diagnosed breast c ancer and 9,138 individually matched controls were included. The unadj usted odds ratio for each marriage after the first was 0.81 [95% confi dence interval (CI) = 0.68-0.97]. After adjustment for major reproduct ive factors, multiple marriages were still found to reduce the risk of breast cancer (odds ratio = 0.86; 95% CI = 0.72-1.03), The findings a re consistent with the operation of an immunologic mechanism in the et iology of breast cancer and suggest that the gene/antigen responsible for this effect is quite common in males. Further empirical evaluation of the fetal antigen hypothesis seems warranted.