MATERNAL PATTERN OF REPRODUCTION AND RISK OF BREAST-CANCER IN DAUGHTERS - RESULTS FROM THE UTAH POPULATION DATABASE

Background: Several studies have found that daughters born to older mothers have an elevated risk of breast cancer, and an endocrine hypothesis, among others, has been developed to explain these findings. Three recent studies have failed to find a consistent maternal age effect, indicating a need for further exploration of this issue. Purpose: We used Utah breast cancer records linked to genealogical records to investigate maternal and paternal age and other maternal reproductive factors in relationship to the daughter's risk of breast cancer. Methods: The study group consisted of 2414 breast cancer case patients and 9138 individually matched control subjects. Breast cancer diagnoses were ascertained through the National Cancer Institute's Surveillance, Epidemiology, and End Results Program. The case patients and control subjects were born between 1875 and the end of 1947, and the mean age at diagnosis of the case patients was 65.9 years. Results: No consistent effect for maternal or paternal age was found, except possibly among women who were firstborn children (odds ratio [OR] = 1.42 for a 10-year differential in maternal age; 95% confidence interval [CI] = 1.00-2.00). Further examination of the data indicated that mothers of case patients experienced long intervals between marriage and their first birth but not between subsequent births, and they went on to have fewer children. For each year of delay between the mother's marriage and first birth, the odds of breast cancer in the daughter increased 1.05-fold (95% CI = 1.01-1.10). Conclusions: We found no evidence of a consistent maternal age effect with regard to breast cancer risk in the daughter, but we did find evidence that the mothers of women who go on to get breast cancer have a reproductive pattern that could suggest some form of underlying infertility. Implications: These findings widen the epidemiologic support for the fetal antigen hypothesis, which is an immunogenetic explanation for the relationships between reproductive factors and breast cancer risk. That hypothesis provides strategies for the identification of breast cancer genes and the eventual development of a breast cancer vaccine.