Effect of obesity on disease-free and overall survival in node-positive breast cancer patients in a large French population: a pooled analysis of two randomised trials.

BACKGROUND: To examine the association between baseline body mass index (BMI), and disease-free survival (DFS) and overall survival (OS) in a large French early-stage breast cancer population included in the UNICANCER Programme d'Action Concerté Sein-01 (PACS01) and PACS04 phase III randomised trials.

METHODS: After a median follow-up of 5.9years, this report analyses 4996 patients with node-positive breast cancer, and randomly assigned to adjuvant anthracycline-based chemotherapy combined or not with taxanes. Univariate analyses were used to study the effects of well known prognostic factors and BMI on DFS and OS. BMI was obtained at baseline, before chemotherapy initiation, and obesity was defined as a BMI⩾30kg/m(2). Cox proportional hazards regression models were secondly used to assess the influence of BMI after adjusting for other factors. Exhaustive analysis of the dose intensity delivered was also studied for comparison between obese and non-obese patients.

RESULTS: Obese patients initially present with more advanced disease at diagnosis compared to non-obese patients. By univariate analysis, obesity was moderately associated with poorer DFS (hazard ratio (HR)=1.18 [1.01-1.39] P=0.04), but mostly with poorer OS (HR=1.38 [1.13-1.69] P=0.002). Delivered dose intensity of anthracyclines and taxanes was not significantly different between obese and non-obese patients. After adjustment for disease characteristics, BMI had no influence either on DFS or OS.

CONCLUSION: This report suggests that in a French population, obesity has no impact on breast cancer prognosis when modern adjuvant chemotherapy, at the appropriate dose intensity, is delivered.