Patterns of Biologics Use Across Treatment Lines in Elderly (Age >65) Medicare Patients With Metastatic Colon Cancer

Background: We explored biologics receipt in metastatic colon cancer.

Methods: We used Surveillance, Epidemiology, and End Results-Medicare data of 4,545 elderly patients diagnosed with incident metastatic colon cancer from 2003 to 2009, treated with chemotherapy and/or biologics, and followed up through 2010.

Results: A total of 2,504 (55%) patients received a biologics-containing regimen. Treatment with biologics fluctuated between 46% and 63% of first-line regimens and 67% and 73% of second-line regimens. Bevacizumab accounted for 95% of first-line and 68% of second-line biologics use. Cetuximab accounted for 33% of second-line and 48% of third-line use. Panitumumab accounted for 5% of second-line and 27% of third-line use. The adjusted odds of biologics receipt decreased rapidly with age, resulting in a threefold difference between the youngest and the oldest study participants in the sample (odds ratio [OR] 0.35, p < .01). African Americans (OR 0.77, p = .03) and patients with Charlson Comorbidity Index of 1 (OR 0.83, p = .02) or >1 (OR 0.75, p < .01) were considerably less likely to receive biologics therapy. Medicare state buy-in was associated with 2% lower odds of receiving biologics (OR 0.98, p = .04).

Conclusion: After controlling for sociodemographic and clinical differences, age, race, comorbidities, and low income had a statistically significantly negative effect on the likelihood of receiving biologics among treated patients. Use of biologics varied over time, across the treatment continuum, and by chemotherapy regimen. Bevacizumab was most frequently used in both first- and second-line treatment. Cetuximab was the second most prescribed biologic. Panitumumab use was mostly limited to third-line treatment.

Implications for practice: It is well-known that patients in the "real world" receive cancer treatments that do not reflect the strict treatment protocols of clinical trials. This is particularly true for complex and elderly patients with metastatic disease, who are frequently underrepresented in clinical trials. Although this article does not provide any additional evidence about the effectiveness of one treatment regimen or treatment sequence over another, it enhances our understanding of oncology practice outside of the clinical trial setting and provides useful information for future health services and health economics research in metastatic colon cancer.