The use of chemotherapy in older patients with stage II and III colon cancer: Variation by age and era of diagnosis

Abstract

Objective: We aim to examine the use and outcomes of adjuvant chemotherapy in older patients with stage II and III colon cancer.

Material and methods: Using data from the SEER-Medicare database, we analyzed patients aged 66 or greater, diagnosed with stage II or III colon cancer between 1991 and 2007 who received surgery. Using Medicare claims, receipt of adjuvant chemotherapy was identified, and compared between age bands. Logistic regression modeling was performed to assess predictors of receipt of adjuvant chemotherapy, and Cox proportional hazards modeling was performed to assess predictors of mortality.

Results: A total of 31,990 patients were identified: 4371 aged 66-69, 6922 (70-74), 7673 (75-79), 6807 (80-84), 4266 (85-89), and 1951 (90+). The percent starting adjuvant chemotherapy decreased by age cohort: 57% in the 66-69 age cohort, 48% (70-74), 37% (75-79), 20% (80-84), 8% (85-89), and 1% (90+). Multivariable analysis showed that stage III disease was the strongest positive predictor of chemotherapy receipt. Multivariable analysis for mortality risk showed that adjuvant chemotherapy was associated with an increased risk of mortality in stage II patients. Adjuvant chemotherapy was associated with a decreased risk of mortality in stage III patients, consistent across all age cohorts, with the exception of the 90+ cohort, in whom adjuvant chemotherapy appeared to increase mortality.

Conclusion: Administration of adjuvant chemotherapy for stage II/III colon cancer decreases with advancing age, but improved outcomes are seen in stage III patients under 90 years of age.

Keywords: Adjuvant; Chemotherapy; Colon cancer; Elderly; Older adults; SEER-Medicare.