Determinants of adjuvant oxaliplatin receipt among older stage II and III colorectal cancer patients.

BACKGROUND: Controversy exists regarding adjuvant oxaliplatin treatment among older patients with stage II and III colorectal cancer (CRC). This study sought to identify patient/tumor, physician, hospital, and geographic factors associated with oxaliplatin use among older patients.
METHODS: Individuals diagnosed at age > 65 with stage II or III CRC from 2004 through 2007 undergoing surgical resection and receiving adjuvant chemotherapy were identified using the Surveillance, Epidemiology and End Results program (SEER)-Medicare database, which includes patient/tumor and hospital characteristics. Physician information was obtained from the American Medical Association. Poisson regression was used to identify independent predictors of oxaliplatin receipt. The discriminatory ability of each category of characteristics to predict oxaliplatin receipt was assessed by comparing the area under the receiver operating curve from logistic regression models.
RESULTS: We identified 4388 individuals who underwent surgical resection at 773 hospitals and received chemotherapy from 1517 physicians. Adjuvant oxaliplatin use was higher among stage III (colon = 56%, rectum = 51%) compared to stage II patients (colon = 37%, rectum = 35%). Overall, patients who were older; diagnosed before 2006; separated, divorced, or widowed; living in a higher poverty census tract or in the East or Midwest; or with higher levels of comorbidity were less likely to receive oxaliplatin. Patient factors and calendar year accounted for most of the variation in oxaliplatin receipt (area under the curve = 75.8%).
CONCLUSIONS: Adjuvant oxaliplatin use increased rapidly from 2004 through 2007 despite uncertainties regarding its effectiveness in older patients. Physician and hospital characteristics had little influence on adjuvant oxaliplatin receipt among older patients.