Efficacy and safety of single agent (SA) or combination (CO) adjuvant chemotherapy (AC) in elderly patients with colon cancer: A Canadian cancer institute experience.

Abstract

581 Background: Although AC is recommended for colon cancer, the pattern of AC use in elderly patients (pts), the toxicity profile, & survival benefit is unclear. We sought to (1)determine whether pts ≥ 65 years old with stage III colon cancer were being offered SA or CO AC; (2)evaluate the reason for selecting SA vs. CO AC; (3)evaluate the toxicity profile of SA and CO in the elderly; and (4)determine whether a survival benefit exists for elderly pts receiving CO AC. Methods: Pts ≥ 65 diagnosed with stage III colon cancer at the Cross Cancer Institute from 2004-2010 were identified from the cancer registry. A retrospective analysis of electronic and paper patient records was performed to identify baseline characteristics, AC protocols used, toxicity, dose intensity and survival. Results: 258 pts ≥ 65 years old were diagnosed and treated with AC from 2004-2010. Of these, 168 were treated with SA and 90 with CO AC. The most common reasons for choosing SA AC were patient preference (64%), comorbidities (10%), and lack of drug coverage by provincial formulary (15%). 93 pts ≥age 75 were treated with SA AC, whereas only 10 pts ≥ 75 were treated with CO AC. Multivariate analysis revealed that for each year above 65, the adjusted odds of receiving CO over SA AC decreased by 22%. The presence of cardiac comorbidities decreased the adjusted odds of receiving CO AC by 58%. 28% of pts treated with SA and 6% of those treated with CO AC had initial dose reductions, with most common reasons being comorbidities and age. 67%, 71%, and 29% received dose delays, reductions or drug discontinuation in the SA group, respectively. 72%, 58%, and 34% received dose delays, reductions or drug discontinuation in the CO group respectively, mostly due to hematologic toxicity. The 5 year OS was 73% in pts who received SA AC, compared to 84% in those who received CO AC. A competing risk analysis showed no difference in cancer-related deaths between the CO and SA AC groups. Conclusions: In elderly pts treated with AC for stage III colon cancer, SA AC is used more frequently than CO AC, based on age, comorbidities, and patient choice. Toxicity with CO AC in elderly pts is high, leading to decreased dose intensity. No survival benefit was seen with CO AC over SA AC.