Preliminary analysis and assessment of breast cancer risk in Japanese women.

e13092 Background: No comprehensive breast cancer risk assessment model for Japanese women exists. Consequently, we have collected Japanese women’s data to investigate key BC risk factors with an objective of deriving a Japanese-women specific BC risk assessment model. Methods: We conducted a retrospective case-control study (paper-based with postal survey) at 15 institutions during 2014-2015. A survey was distributed to Japanese females aged 20-80 who had BC check-up. All pertinent data of a total of 34 factors including demographic and reproductive factors, social history and eating habits was collected. Cases and controls were divided into three groups respectively, premenopausal (PRE; 20 ≤ age < 45), perimenopausal (PERI; 45 ≤ age ≤ 55) and postmenopausal group (POST; 55 < age ≤ 80). Cases and control variables were compared by t-test, chi-square test and Wilcoxon rank sum test. Preliminary BC risk was calculated by logistic regression analysis. Results: A total of 3975 female Japanese datasets were collected, of which 2494 were complete (all variables present) with 1401 controls and 1093 cases were used. There were 222 cases and 332 controls for PRE, 404 cases and 537 controls for PERI, and 467 and 532 controls for POST. The univariate analysis demonstrated that BMI was significantly higher in cases than in controls in all groups (P < 0.01) as was “number of deliveries” in PRE and POST (P < 0.001) and Brinkman index in PRE and PERI (p = 0.017). Multivariate analysis revealed that BC risk was positively associated with BMI (OR 1.080, 95% CI 1.017–1.148, p = 0.012) in PRE, BMI (OR 1.121, 95% CI 1.072–1.174, p < 0.01) and brinkman index (OR 1.000005, 95% CI 1.000002–1.000008, p < 0.01) in PERI, age (OR 1.054, 95% CI 1.028–1.081, p < 0.010), BMI (OR 1.153, 95% CI 1.076-1.171, p < 0.01) and family history (OR 1.497, 95% CI 1.103–2.033, p = 0.001) in POST, while negatively associated with regular exercise (OR 0.672, 95% CI 0.517–0.873, p = 0.003) in POST. Conclusions: BMI in all groups, in addition, the Brinkman index in PERI and age and family history in POST are BC risk factors. Exercise is a protective risk factor in POST. However, the preliminary results are incomplete and further analysis will be conducted before a full risk assessment model is proposed for Japanese women.