The impact of chronic illnesses on the use and effectiveness of adjuvant chemotherapy for colon cancer

BACKGROUND. It is unclear how noricancer conditions affect the use or effectiveness of adjuvant therapy among older patients with colon cancer. METHODS. The authors conducted a cohort study of older patients with stage III colon cancer who were diagnosed from 1993 to 1999 in the Surveillance, Epidemiology, and End Results -Medicare database. The correlations between receipt of adjuvant chemotherapy and heart failure, diabetes, and chronic obstructive pulmonary disease (COPD) were assessed. Multivariable regression analysis was used to assess the risk of death and hospitalization as a function of treatment and comorbidity status. RESULTS. The study sample consisted of 5330 patients (median age, 76 years). The use of adjuvant therapy was related significantly to heart failure (36.2% vs 64.9% of patients with vs without heart failure, respectively; adjusted odds ratio [OR], 0.49; 95% confidence interval [95% CI], 0.40-0.60). More moderate correlations were observed for COPD (OR, 0.83; 95% CI, 0.70-0.99) and diabetes (OR, 0.81; 95% CI, 0.68-0.97). Among patients who had heart failure, the 5-year survival was significantly higher among those who received adjuvant chemotherapy (adjusted 5-year survival rate, 43%; 95% CI, 40-47%) than among those who did not receive adjuvant chemotherapy (30%; 95% CI, 27-34%). Among patients without heart failure, the 5-year survival estimates among treated and untreated patients were 54% (95% CI, 52-56%) and 41% (95% CI, 38-44%), respectively. The probability of A-cause, condition-specific, or toxicity-related hospitalization associated with adjuvant therapy was not altered by the presence of any of the 3 conditions. CONCLUSIONS. Although chronic conditions appeared to be a strong barrier to the receipt of adjuvant chemotherapy, adjuvant therapy appeared to provide a significant survival benefit to patients who had colon cancer with the conditions studied.