Is BMD (Bone Mineral Density) a prognostic factor for luminal A breast cancer in postmenopausal women?

e12542 Background: There are some studies concerned about the relationship of BMD (Bone Mineral Density) and breast cancer risks in menopausal women. However, most studies have limitations in that they did not distinguish the subtypes of breast cancer. Therefore, we assessed the BMD as a risk factor of recurrences, metastases, or occurrences of contralateral breast cancer in the luminal A breast cancer patients with menopause. Methods: In this retrospective study, the data of 348 luminal A type breast cancer patients, who underwent treatment at the Pusan National University Yangsan Hospital from 2012 to 2016, were analyzed. BMD of the lumbar spine, total femur, and femoral neck was measured by Dual Energy X-ray Absorptiometry (DXA). According to the measured BMD and WHO criteria, the group with T scores ≥ -1.0 was defined as normal, the group with T scores < -1.0 and > -2.5 was defined as osteopenia, and the group with T scores < -2.5 was defined as osteoporosis. The patients were divided into two groups: those with normal BMD and those with low BMD including osteopenia or osteoporosis in preoperative examination. We also divided patients as three groups: one group with no change of BMD, the other group with improvement of BMD and the other with deterioration of BMD during treatment. We used Chi-squared tests, Kaplan-Meier method and Cox-regression model to analyze the relationship between BMD and breast cancer risk. Results: Among the 348 patients, normal BMD was confirmed by preoperative examination in 129 patients and low BMD was identified in 219 patients. There was no change in BMD during the treatment in 243 patients. The improvement in BMD was identified in 37 patients, and the deterioration of BMD was confirmed in 68 patients. Younger patients were distributed in normal BMD compared to low BMD (55.7±6.9 vs 61.8±8.0, p<0.05). There were only 14 patients (4.0%) with recurrences, distant metastases or occurrences of contralateral breast cancer during a median follow-up period of 78 months. Among the 219 patients with low BMD, disease-free survival at 5 years was 98.2% compared to 95.0% for 129 patients with normal BMD ( p=0.326). In addition, disease-free survival at 5-years was 97.0% in no change of BMD during treatment, 94.6% in improvement of BMD, and 98.4% in deterioration of BMD ( p=0.785). Conclusions: In this study, BMD did not have statistically significance in the recurrences, metastases, or occurrences of contralateral breast cancer in luminal A breast cancer patients with menopause. In addition, there was no statistically importance in relationship between BMD change during treatment and recurrences, metastases, or occurrences of contralateral breast cancer. Therefore, we should perform treatments to breast cancer patients preventing decreased BMD.