Purpose: Drugs are usually approved for a specific indication on the basis of randomized trials. However, once approved, these treatments are often used differently than as tested in trials. We performed an analysis to determine the patterns of use of erythropoiesis-stimulating agents (ESAs).
Methods: We used the Surveillance, Epidemiology, and End Results-Medicare database to identify patients age 65 years or older with breast, lung, or colon cancer diagnosed between 1995 and 2005 who had one ESA and chemotherapy claim. Associations of patient, tumor, and physician-related factors with receipt of ESAs were analyzed.
Results: Of 21,091 patients analyzed, 5,099 (24.2%) received ESAs for 1 week or less (misuse), and 1,601 (7.6%) received ESAs for more than 14 weeks (prolonged use). Receipt of ESAs while not actively receiving chemotherapy (off label) occurred in 2,876 patients (13.6%). In a multivariable analysis, ESA misuse was associated with MD degree, female sex of physician, and earlier year of medical school graduation. Private practice physicians (odds ratio [OR], 0.78; 95% CI, 0.72 to 0.84) and high-volume physicians (OR, 0.78; 95% CI, 0.72 to 0.85) were less likely to use 1 week or less of ESA treatment. Treatment by high-volume oncologists (OR, 1.33; 95% CI, 1.14 to 1.55) and by oncologists who graduated from US medical schools (OR, 1.26; 95% CI, 1.12 to 1.42) predicted prolonged-duration ESA use, whereas female oncologists (OR, 0.79; 95% CI, 0.68 to 0.93) were less likely to prescribe prolonged ESA treatment. Private practice physicians (OR, 1.18; 95% CI, 1.02 to 1.38) and high-volume providers (OR, 1.58; 95% CI, 1.33 to 1.87) were more likely to prescribe more than 24 weeks of ESA treatment.
Conclusion: Our study demonstrated widespread variability in the use of ESAs. Physician characteristics exerted substantial influence on ESA use. Policies to discourage inappropriate use of cancer therapies are needed.