Uptake of bevacizumab for the treatment of colon cancer.

Abstract

6107 Background: While bevacizumab (BEV) has been shown to improve mortality when added to first-line treatment of metastatic colon cancer, a randomized trial presented at ASCO 2009 reported no benefit from the addition of BEV in stage III colon cancer. We investigated the uptake of BEV for the treatment of both early stage and metastatic colon cancer in a population-based sample. Methods: We identified patients >65 yrs diagnosed with stage III colon cancer, 9/1/04-12/31/05, in the SEER-Medicare database who were treated within 6 months of diagnosis. We also identified patients >65 yrs diagnosed with stage IV or recurrent colon cancer, 1/1/05-12/31/05. We used multivariable logistic regression models and Generalized Estimating Equations to assess the relationship between patient/physician characteristics and receipt of BEV for the metastatic cohort. Results: Among 1884 patients with stage III colon cancer, 825 (43.8%) were treated with chemotherapy of whom 55 (6.7%) had claims for BEV. Among 1,119 patients with stage IV or recurrent colon cancer, 441 (39.4%) had claims for chemotherapy, and of these, 312 (70.7%) had claims for BEV. Among 859 (76.8%) patients with metastatic disease seen by an oncologist, we found that younger age (OR 5.31 95%CI 3.02-9.35), being married (OR 1.72 95% CI 1.17-2.52), and fewer comorbidities (OR 2.04 95% CI 1.19-3.52) were associated with receipt of both chemotherapy and BEV, when compared to patients who received no chemotherapy. Patients who had younger physicians (OR 3.31 95%CI 1.92-5.73), US trained physicians (OR 1.47 95% CI 1.03-2.12), and physicians who treated more patients in our sample (OR 1.69 95% CI 1.19-2.41) were also more likely to receive chemotherapy with BEV. Among metastatic patients who received chemotherapy, we found that having no comorbidities (OR 2.33 95% CI 1.41-3.85), a male physician (OR 1.88 95%CI 1.14-3.12) and a physician who treated more patients in our cohort (OR 1.61 95%CI 1.02-2.54) were all associated with the additional receipt of BEV compared to no BEV. Conclusions: For patients with metastatic colon cancer treated with chemotherapy, uptake of BEV was very rapid, and influenced by physician characteristics. Despite a lack of efficacy, patients were also receiving it off-label in the adjuvant setting.