Interaction between Family History of Breast Cancer and the Remaining Gail Risk Factors.

Abstract

Abstract Background: The Gail breast cancer risk assessment model takes into account the relative contribution of various breast cancer risk factors (RF) and provides 5-year and lifetime breast cancer risk estimates. The purpose of this analysis was to determine the relative contribution of the Gail model RF in patients with and without family history of breast cancer (FHBC).Materials and Methods: Patients from the RUTH trial, consisting of postmenopausal women with or at high risk for coronary artery disease (CAD), were included in this analysis, with the exception of women ≥86 years of age or with medical history of any breast cancer, ductal carcinoma in situ, or lobular carcinoma in situ. Patients with missing values for RF were also excluded. For the resulting study population (N=10015), the risk score was calculated using the breast cancer risk assessment (BCRA) tool from the National Cancer Institute. A descriptive analysis of the BCRA risk scores for each RF stratified based on the presence or absence of a FHBC was performed. Risk factors were categorized as follows: advancing age (<65 or ≥65; 65 was the mean age); age at menarche (>12 or ≤12), number of biopsies (None or ≥1), age at first live child birth (<30 or ≥30; nulliparty included in <30 group per model). Interaction plots based on the two-way analysis of variance (ANOVA) model were generated for each category of the RF.Results: Of the 10015 women, 9123 (91.1%) did not have FHBC, while 892 (8.9%) did. Among women without FHBC, the mean BCRA score (%) was 1.54±0.40; 62.2% were 65 years or older, 28.8% had early menarche, 8.4% had first child at ≥30 years of age, and 8.1% had a previous breast biopsy. Among women with FHBC, mean BCRA score was 3.46±1.24; 70.3% were 65 years or older, 30.4% had early menarche, 9.3% had first child at ≥30 years of age, and 15.4 % had a previous breast biopsy. A statistically significant (p<0.001) amplification in the risk conferred by advancing age, previous biopsy, and early menarche was observed in patients with FHBC compared with patients with no family history for the disease (Figure 1). In contrast, the relative contribution to risk by late childbearing is more pronounced (p<0.001) in patients without FHBC.Discussion: Family history is an independent and important determinant of breast cancer risk in postmenopausal women. Other RF have a different influence on the overall risk estimate in women with FHBC when compared to women without FHBC. Increased risk was observed for advancing age, early menarche, and previous breast biopsy. A different pattern was seen for late childbearing. While the data were obtained from a large cohort of women, further analysis may be required to determine if these results are generalizable for all women regardless of menopausal status or CAD.Figure 1. Mean BCRA risk within each risk factor group, stratified by FHBC. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6062.