Search

Background: As women age, the lobules in their breasts undergo involution or regression. We investigated whether lobular involution in women with benign breast disease was associated with subsequent breast cancer risk., Methods: We examined biopsy specimens of 8736 women in the Mayo Benign Breast Disease Cohort from whom biopsy samples were taken between January 1, 1967, and December 31, 1991. Median follow-up for breast cancer outcomes was 17 years. We classified lobular involution in the background breast tissue as none (0% involuted lobules), partial (1%-74%), or complete (> or = 75%). Subsequent breast cancer events and data on other risk factors were obtained from medical records and follow-up questionnaires. To estimate relative risks (RRs), standardized incidence ratios were calculated by use of incidence rates from the Iowa Surveillance, Epidemiology, and End Results (SEER) Registry. All statistical tests were two-sided., Results: Distribution of extent of involution was none among 1627 (18.6%) women, partial among 5197 (59.5%), and complete among 1912 (21.9%). Increased involution was positively associated with increased age and inversely associated with parity (both P<.001). The relative risk for the entire cohort of 8736 women, compared with the Iowa SEER population, was 1.40 (95% CI = 1.30 to 1.51). Risk of breast cancer was associated with the extent of involution (for no involution, RR [i.e., observed versus expected] = 1.88, 95% confidence interval [CI] = 1.59 to 2.21; for partial involution, RR = 1.47, 95% CI = 1.33 to 1.61; and for complete involution, RR = 0.91, 95% CI = 0.75 to 1.10; test for heterogeneity P<.001). Lobular involution modified risk in all subsets (e.g., among women with atypia, for no involution, RR = 7.79, 95% CI = 3.56 to 14.81; for partial involution, RR = 4.06, 95% CI = 3.03 to 5.33; and for complete involution, RR = 1.49, 95% CI = 0.41 to 3.82; P = .003)., Conclusions: In this large cohort of women with benign breast disease, lobular involution was associated with reduced risk of breast cancer. Aberrant involution may be a biologically important phenomenon in breast cancer biology.

Alcohol intake is an established risk factor for breast cancer, but the underlying mechanism remains unknown. Four recent studies have described interactions of alcohol and low folate intake. We examined this interaction on the risk of postmenopausal breast cancer stratified by tumor receptor status for estrogen (ER) and progesterone (PR). The Iowa Women's Health Study is a prospective cohort study of 34,393 at-risk women. Alcohol use and folate intake from diet and supplements were estimated at baseline in 1986 through a semiquantitative food frequency questionnaire. Through 1999, 1,875 cases of breast cancer were identified through linkage to the Iowa Surveillance, Epidemiology, and End Results registry. Compared with nondrinkers with folate intakes above the 50(th) percentile, women with low folate and high alcohol were at 1.43-fold greater risk (1.02-2.02). When stratified by tumor receptor status for ER or PR, the risks for low folate/high alcohol were 2.1 (1.18-3.85), 1.0 (0.76-1.42), 1.2 (0.88-1.70), and 1.2 (0.69-2.02) for ER-, ER+, PR+, and PR- tumors, respectively. Because the results were limited primarily to ER- tumors, one plausible interpretation of these data is that alcohol influences breast cancer through its metabolite, acetaldehyde, rather than through effects on ER levels and receptor-mediated pathways.

The authors previously reported an interaction of waist/hip ratio and family history on the risk of breast cancer in the Iowa Women's Health Study. Here they reexamine this association based on 9 additional years of follow-up, stratifying on tumor receptors for estrogen and progesterone. Data on risk factors and family history of breast cancer were ascertained in 1986. The occurrences of breast cancer and estrogen receptor/progesterone receptor were determined through the Iowa Surveillance, Epidemiology, and End Results' registry. Rate ratios were elevated with increasing weight and body mass index and decreasing body mass index at age 18 years, but they did not vary by family history. There was no association with height, waist circumference, or waist/hip ratio. A linear trend of increasing risk with increasing waist/hip ratio was observed among family history-positive women (p = 0.06) but not among family history-negative women (p = 0.87). This apparent interaction (p = 0.09) was examined by estrogen receptor or progesterone receptor status. When stratified on family history and estrogen receptor, no clear patterns were evident. In contrast, family history-positive women in the upper quintile of the waist/hip ratio were at 2.2-fold greater risk of progesterone receptor-negative tumors compared with those in the lowest quintile (95% confidence interval: 0.9, 5.8). Thus, the previously reported interaction between family history and waist/hip ratio is still (weakly) evident and appears to reflect risk for progesterone receptor-negative tumors.