Adjuvant chemotherapy for stage III colon cancer in the oldest old: results beyond clinical guidelines.

BACKGROUND: Randomized trials demonstrating the benefits of chemotherapy in patients with American Joint Committee on Cancer stage III colon cancer underrepresent persons aged = 75 years. The generalizability of these studies to a growing elderly population remains unknown. METHODS: Using the California Cancer Registry for 1994 through 2008, the authors conducted a population-based study of postcolectomy patients aged 50 years to 94 years with stage III (N1M0) colon adenocarcinoma. A 2-sided chi-square test and Cochran-Armitage test for trend were used to compare patient and tumor characteristics associated with receipt of chemotherapy across age groups. Multivariate regression was used to assess the association between older age and receipt of chemotherapy. Kaplan-Meier methods and Cox proportional hazards modeling were used to evaluate the association between chemotherapy and mortality, with propensity score adjustment. RESULTS: Approximately 44% (12,382 patients) of the study cohort was aged = 75 years. Persons aged = 75 years were found to be less likely to have received adjuvant chemotherapy than those aged < 75 years (30% vs 68% in patients aged 50 years-74 years; P < .0001). On multivariate analysis, patients aged 75 years to 84 years were 13 times less likely, and those aged 85 years to 94 years were 24 times less likely, to have received chemotherapy as patients aged 50 years to 64 years. Nevertheless, age-stratified multivariate survival analyses indicated that chemotherapy provided comparable mortality reduction across age groups. CONCLUSIONS: The percentage of persons aged = 75 years receiving adjuvant chemotherapy remains low despite demonstrated survival benefits. These findings deserve attention within the context of a patient's life expectancy, underlying comorbidities, and performance status, as well as clinician bias. The results of the current study support the call for phase II/III studies assessing the toxicities and benefits of adjuvant chemotherapy for the treatment of stage III colon cancer in the elderly. Cancer 2013. (c) 2012 American Cancer Society