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 mo thers have an elevated risk of breast cancer, and an endocrine hypothe sis, 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 u sed Utah breast cancer records linked to genealogical records to inves tigate maternal and paternal age and other maternal reproductive facto rs in relationship to the daughter's risk of breast cancer. Methods: T he study group consisted of 2414 breast cancer case patients and 9138 individually matched control subjects. Breast cancer diagnoses were as certained through the National Cancer Institute's Surveillance, Epidem iology, and End Results Program. The case patients and control subject s were born between 1875 and the end of 1947, and the mean age at diag nosis of the case patients was 65.9 years. Results: No consistent effe ct for maternal or paternal age was found, except possibly among women who were firstborn children (odds ratio [OR] = 1.42 for a 10-year dif ferential in maternal age; 95% confidence interval [CI] = 1.00-2.00). Further examination of the data indicated that mothers of case patient s experienced long intervals between marriage and their first birth bu t not between subsequent births, and they went on to have fewer childr en. For each year of delay between the mother's marriage and first bir th, 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 ma ternal age effect with regard to breast cancer risk in the daughter, b ut we did find evidence that the mothers of women who go on to get bre ast cancer have a reproductive pattern that could suggest some form of underlying infertility. Implications: These findings widen the epidem iologic support for the fetal antigen hypothesis, which is an immunoge netic explanation for the relationships between reproductive factors a nd breast cancer risk. That hypothesis provides strategies for the ide ntification of breast cancer genes and the eventual development of a b reast cancer vaccine.