posters International Association for Breast Cancer Research 2014

Mammographic density and breast cancer risk by family history in women of white and Asian ancestry (#56)

Gertraud Maskarinec 1 , Christy G. Woolcott 2 , Shannon M. Conroy 3 , Celia Byrne 4 , Chisato Nagata 5 , Giske Ursin 6 , Celine M. Vachon 7
  1. University of Hawaii, Honolulu, HI, United States
  2. Dalhousie University, Halifax, NS, Canada
  3. California Department of Health, Sacramento, CA, USA
  4. Uniformed Services University of the Health Sciences, Bethesda, MD, USA
  5. Gifu University Graduate School of Medicine, Gifu, Japan
  6. Cancer Registry of Norway, Oslo, Norway
  7. Mayo Clinic, Rochester, MN, USA
Genetic factors related to mammographic density might also be associated with familial risk of breast cancer. To determine whether the association of mammographic density with breast cancer risk differed by family history of breast cancer (FHBC) in women of white and Asian ancestry, we analyzed data from four case-control studies conducted in the United States and in Japan. To standardize mammographic density assessment, a single observer re-read all mammograms using one type of interactive thresholding software. Logistic regression was applied to estimate odds ratios (OR) while adjusting for known confounders. The study population included 1699 breast cancer cases and 2422 controls, 45% of whom were white (N=1849) and 40% Asian (N=1633), primarily Japanese. Overall, 12% of participants reported a FHBC with a lower proportion in Japan (5%) than California (13%), Hawaii (14%), and Minnesota (14%). FHBC was significantly associated with breast cancer risk in the adjusted model (OR=1.51; 95%CI: 1.24-1.84). The interaction terms of percent density (per 10%) with FHBC (p=0.03) and ethnicity (p=0.01) were statistically significant. The OR associated with a 10% increase in PD was higher for women with a FHBC (OR=1.30; 95%CI: 1.13-1.49) than for those without (OR=1.14; 1.09-1.20). After stratification by ethnicity, this pattern was also apparent in whites and Asians with ORs of 1.45 (95%CI: 1.17-1.80) vs. 1.22 (95%CI: 1.14-1.32) and 1.24 (95%CI: 0.97-1.58) vs. 1.09 (95%CI: 1.00-1.19). Results were similar for dense area (per 10 cm2, square-root transformed) although the interaction term was borderline (p=0.10). The respective risk estimates for women with and without a FHBC were (OR=2.12; 95%CI: 1.47-3.06) and (OR=1.51; 95%CI: 1.33-1.71). In conclusion, women with a FHBC have a higher risk than women without. Also, white women have a higher risk than Asian women. These findings support the hypothesis that FHBC and ethnicity modify breast cancer risk attributable to mammographic density.