Effect of body mass index on the efficacy of adjuvant tamoxifen in premenopausal patients with hormone receptor-positive breast cancer

Purpose: Obesity has been confirmed to be an adverse prognostic factor in patients who were treated with aromatase inhibitors; however, such relationship has never been thoroughly investigated in patients treated with tamoxifen. The purpose of this study was to examine the effect of body mass index (BMI) on the efficacy of adjuvant tamoxifen in premenopausal patients with hormone receptor-positive breast cancer. Methods: Newly diagnosed premenopausal and non-metastatic hormone receptor-positive breast cancer patients were enrolled in the study. Patients with BMI ranging between 18.5 and 24.9 kg/m(2) were considered as normal weight patients (Arm A, n = 408), and patients with a BMI 25 kg/m(2) were considered as overweight and obese patients (Arm B, n = 418). Results: In both normal weight and overweight patients, the baseline clinicopathologic properties and the treatment history with radiotherapy and chemotherapy were similar and no statistical significant difference could be detected. Tamoxifen in combination with luteinizing hormone-releasing hormone (LHRH) agonist was used in 33% (136/408) of the patients in Arm A and in 22% (91/418) of patients in Arm B (p<0.001). Three-year disease free survival (DFS) rates were 89% and 87% in arm A and arm B, respectively (p=0.39). Three-year overall survival (OS) rates were 99% in arm A and 94% in arm B which appeared to be of significance (p=0.028). In univariate analysis no statistical significant effect of LHRH agonist usage on DFS (p=0.58) and OS (p=0.96) was found. Conclusion: Although BMI had no negative effect on recurrence risk, poor OS was observed in overweight and obese premenopausal breast cancer patients with hormone-receptor positive tumors who were treated with tamoxifen.