Abstract B4: Impact of obesity on the effectiveness of aromatase inhibitors (AIs): Can breast cancer survivors on AIs lose weight compared to non-AI users?

Abstract

Abstract Background and Objectives: Weight at diagnosis and weight gain after diagnosis are associated with increased risk of breast cancer (BrCa) recurrence and mortality. In addition, post-menopausal obese breast cancer survivors on anti-hormonal therapy were 40% more likely to develop a local recurrence and 46% more likely to develop a distant recurrence compared to their normal weight counterparts. This evaluation was conducted to examine if a diet/exercise/behavioral weight loss intervention for overweight breast cancer survivors: 1) would impact BrCa risk biomarkers and 2) would the response differ by aromatase inhibitor (AI) status. Methods: 84 BrCa survivors with a BMI 25-45 kg/m,2 ≥3 months from chemotherapy were recruited, and 52 agreed to participate. 6 (11%) participants did not complete the intervention. The 6-month intervention included: 225 minutes/week of aerobic exercise, resistance training, 1200-1500 calorie/day diet, and weekly group behavioral meetings. Pre and postintervention assessments included: anthropometrics (weight, BMI), body composition (DEXA % body fat), and serum biomarkers (estradiol, testosterone, SHBG, IGF-1/IGFBP3, insulin, leptin, adiponectin, glucose, CRP, cholesterol). Results are shown for 52 women (median age 52 ± 8 years) who initiated the program and 45 (87%) who completed the 6-month intervention. Results: Women were approximately 4.25 years from diagnosis, their median weight at diagnosis was 84.1 kg (±15.8), and BMI was 31.3 kg/m2 (±5.6). Median pre-intervention weight was 91.8 kg (±13.4) and participants lost an average of 10.6 kg (±6.0)* or 13.3% (±28.8)* of their starting weight after the 6-month intervention. BMI decreased from 32.6 kg/m2 (±4.7) to 28.2 kg/m2 (±4.7)* and total percent body fat decreased by 5.6% (±4.5)*. Favorable changes in serum biomarkers of BrCa risk were observed for insulin*, leptin*, adiponectin*, and estradiol*. When comparing AI users to nonusers the significant favorable change in estradiol was not seen for those on AI's. There was a significant difference in decrease in % body fat* between AI users and nonusers. No other differences were significant. (*p-values <0.05) Conclusions: Overall, results suggest a 6-month diet/exercise/behavioral weight loss intervention in overweight post-menopausal BrCa survivors results in a significant decrease in weight and change in serum biomarkers of BrCa risk in both current AI users and nonusers, however, due to the small sample size significant between group difference were not seen. Larger studies evaluating the effects of weight and weight loss based on exposure to antihormonal therapy are needed. Citation Information: Cancer Prev Res 2010;3(12 Suppl):B4.