Body mass index and prognosis of metastatic breast cancer patients receiving first line chemotherapy

Background: The effect of body mass index (BMI) on the prognosis of metastatic breast cancer (MBC) has not been explored so far. Methods: The relationship between BMI (kg/m2), and progression free (PFS) or overall survival (OS) was assessed in 489 MBC patients enrolled in 3 clinical trials of first line chemotherapy. WHO BMI categories were used: normal 18.5-24.9 kg/m2, overweight 25-29.9 kg/m2, obese 30+ kg/m2. Univariate PFS and OS curves were estimated; multivariate Cox analysis was performed adjusting for age, menopausal status, PS, hormonal status and site and number of metastases. Results: Overall, 39.9% of the patients were normal or underweight, 37.8% were overweight and 22.3% were obese. Median age was 57 years (range 25-73); median performance status (PS) was 0. Median PFS was 10.9 months (IQR 5.5 to 19.9) in normal weight women, 13.0 months (IQR 7.8 to 23.7) in overweight and 12.2 (IQR 7.1 to 23.0) in obese women, p=0.17. Median OS was 32.0 months (95% CI 14.5-88.3), versus 33.2 (95% CI 19.4-81.1) and 30.7 (95% CI 17.6-50.8) respectively. In multivariate analyses, no statistically significant association between BMI category and PFS or OS was observed. Conclusions: In this study BMI was not associated with the outcome of MBC patients treated with first line chemotherapy. Impact: The absence of any evidence in support of a prognostic role of obesity in MBC patients treated with chemotherapy, dietary restrictions, medical interventions aimed at reducing BMI/insulin resistance, or specific anticancer treatment strategies do not seem to be appropriate.