Influence of body mass index on outcome in advanced colorectal cancer patients receiving chemotherapy with or without targeted therapy

Abstract Purpose Obesity is associated with an increased risk of development and recurrence of colorectal cancer. However, the role of obesity in advanced colorectal cancer (ACC) patients is unknown. We investigated the effect of body mass index (BMI) on overall survival (OS) in ACC patients receiving systemic treatment in two large phase III studies (CAIRO and CAIRO2). Patients and methods Treatment data were obtained and analysed from 796 ACC patients who were treated with chemotherapy in the CAIRO study, and from 730 ACC patients who were treated with chemotherapy plus targeted therapy in the CAIRO2 study. Baseline height and weight were used to assign patients to one of the following BMI categories: A ( 2 ), B (18.5–24.9 kg/m 2 ), C (25.0–29.9 kg/m 2 ) and D (⩾30.0 kg/m 2 ). Results In 796 patients of the CAIRO study a high BMI was associated with better median OS (8.0, 14.9, 18.4 and 19.5 months for BMI categories A, B, C, and D, respectively; P  = 0.001), and was an independent prognostic factor for OS in a multivariate analysis. BMI was not associated with OS in 730 patients who participated in the CAIRO2 study, although a trend was observed. Conclusions These results show that BMI is an independent prognostic factor for survival in patients receiving chemotherapy, but not in patients receiving chemotherapy and targeted therapy. The possible decreased efficacy of bevacizumab in obese patients may explain this discrepant result. The role of BMI in patients receiving targeted therapy should be further tested.