Abstract P1-09-33: Weight loss and bone health in postmenopausal breast cancer survivors

Abstract

Abstract Background: The importance of bone health among postmenopausal breast cancer survivors cannot be overemphasized. In addition to bone loss due to aging, secondary bone loss resulting from treatment is a major concern. Although weight loss has adverse effects on bone health in postmenopausal women without cancer, the impact of weight loss on bone health in postmenopausal women with breast cancer is not known. Our objective in this study was to evaluate the effect of weight loss on bone health among overweight/obese postmenopausal breast cancer survivors participating in a weight loss trial. Methods: We conducted this study in a subset of women (postmenopausal, N=81) enrolled in the multi-site Exercise and Nutrition to Enhance Recovery and Good health for You (ENERGY) study. The ENERGY study is a randomized controlled clinical trial designed to achieve a sustained ≥7% loss in body weight among overweight/obese breast cancer survivors with stage I, II or IIIA disease. Weight loss was achieved largely through dietary modification with the addition of physical activity. Bone health was assessed in a subset of women at a single site using bone turnover markers (BTMs) and dual energy X-ray absorptiometry (DXA). Markers of bone formation: osteocalcin, bone-specific alkaline phosphatase (BALP), procollagen type I N-terminal propeptide (PINP) and bone resorption: N-telopeptides of type-I collagen (NTX), C-terminal telopeptide (CTX) were quantified in blood samples collected at baseline, 6 month and 12-month follow-up. DXA T-score was used to measure bone mineral density at baseline and at 12-month follow-up. Generalized estimating equations were used to assess differences in mean values over time as well as from baseline to 6- and 12-month follow-up. Data from intervention and control arm women were used and treated as a cohort. Results: The mean age and body mass index (BMI) of women enrolled in our sub-study were 56 years and 31.6kg/m2, respectively. Majority (54.3%) had stage 2 disease. Mean weight decreased by 5.6 pounds between baseline and 6-month follow-up and 4.3 pounds between baseline and 12-month follow-up. There were statistically significant decreases in mean osteocalcin (2.0ng/ml, p-value<0.001), PINP (7.9ng/ml, p-value<0.001) and NTx (3.65nM BCE/L, p-value<0.001), but not BALP and CTX-1 levels between baseline and 12-month follow-up. No significant changes were observed in mean T-scores, pelvis and lumbar spine bone mineral densities between baseline and 12-month follow-up. Weight change from baseline to 12-month follow-up was weakly inversely associated with changes in DXA T-score (r=-0.25, p-value=0.04) and CTX (r=-0.22, p-value=0.07) but not with other BTMs over the same time period. Conclusion: Weight loss over a 12-month period was associated with decreases in markers of bone formation and resorption but no changes in BMD in overweight/obese postmenopausal women with stage I, II or IIIA breast cancer. Further studies on the association of weight loss and the possible modifying effect of physical activity are needed in order to personalize weight control strategies in overweight/obese breast cancer survivors. Citation Format: Adetunji T Toriola, Jingxia Liu, Patricia A Ganz, Graham A Colditz, Lin Yang, Sonya Izadi, Anna L Schwartz, Kathleen Y Wolin. Weight loss and bone health in postmenopausal breast cancer survivors [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-09-33.