Background: Since the introduction of biologic therapies for the treatment of metastatic colorectal cancer (mCRC), few studies have examined patterns of care or predictors of specific treatment approaches.
Methods: We assessed 4877 mCRC patients who received chemotherapy between January 2004 and March 2011 at academic, private, and community-based oncology practices subscribing to a US-wide chemotherapy order entry (system capturing disease, patient, provider, and treatment data. Multivariable analyses of these prospectively recorded characteristics were used to identify independent predictors of specific therapeutic choices. All statistical tests were two-sided.
Results: Throughout the study period, fluoropyrimidine/oxaliplatin combination was the most commonly used first-line chemotherapy regimen, representing 71% of first-line therapy by 2007. First-line bevacizumab use averaged 51%, peaking at 55% in 2006. Of those who received first-line bevacizumab, 34% continued to receive bevacizumab in the second-line. Only 26% of patients in our cohort ever received an anti-EGFR monoclonal antibody (cetuximab = 22%; panitumumab = 6%) at some point in their treatment course. Patients treated at academic centers, with longer duration of first-line therapy, and at sites in the western United States were statistically more likely to receive an anti-EGFR antibody. Anti-EGFR antibody use fell by 18% after the US Food and Drug Administration limited its use to patients with KRAS wild-type tumors in June 2009.
Conclusions: Analysis of this US-wide mCRC cohort demonstrates that bevacizumab has been more consistently integrated into treatment regimens than anti-EGFR antibody therapies, particularly in first-line therapy. However, treatment choices vary substantially according to specific patient, practice, and provider characteristics.