FOLFOX and FOLFIRI Use in Stage IV Colon Cancer: Analysis of SEER-Medicare Data.

BACKGROUND: Shortly after the year 2000, randomized trials demonstrated that patients with metastatic colon cancer treated with infusional 5-fluorouracil (5-FU)/leucovorin with either oxaliplatin (FOLFOX) or irinotecan (FOLFIRI) had a comparable progression-free survival benefit, superior to patients who received 5-FU/leucovorin alone. Factors associated with the initial receipt of the FOLFOX or FOLFIRI regimen are unknown. Our goal was to investigate the patterns and predictors of use for first-line FOLFOX and FOLFIRI.

PATIENTS AND METHODS: We used the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked data set to identify patients with newly diagnosed stage IV colon cancer between the years 2005 and 2013 who received either first-line FOLFOX or FOLFIRI. We used logistic regression to assess demographic and clinical predictors for FOLFOX versus FOLFIRI. Survival was compared by Kaplan-Meier models.

RESULTS: Overall, 3000 patients (79.3%) received FOLFOX and 785 (20.7%) FOLFIRI. FOLFOX was associated with later year of diagnosis (odds ratio [OR] = 0.66, 95% confidence interval [CI], 0.54 to 0.82 for 2011-2013 vs. 2005-2007), being female (OR = 0.82; 95% CI 0.69 to 0.98), and living in the southern region of the United States. FOLFIRI was associated with having a higher comorbidity index (OR = 1.33; 95% CI, 1.07 to 1.67 for >1 comorbidity score vs. 0). There was no survival difference observed between the two treatments.

CONCLUSION: The majority of SEER-Medicare patients received FOLFOX and not FOLFIRI as a first-line treatment for stage IV colon cancer. Several demographic and clinical factors were associated with the use of each specific regimen. No survival difference was detected for the 2 groups.