Predictors of second- and third-line chemotherapy receipt in stage IV colon cancer Medicare beneficiaries.

Abstract

588 Background: The prognosis for elderly patients with metastatic colon cancer (mCC) is poor with 5-year survival rate of 6 %. There is limited evidence to explain why some elderly mCC patients progress through multiple lines of treatment and others with similar clinical characteristics do not. This study examines the predictors of second- and third-line chemotherapy receipts in Medicare beneficiaries with mCC who initiate treatment. Methods: Using the SEER-Medicare dataset, elderly beneficiaries diagnosed with mCC from 2003-2007, were followed until death or censoring in 2009. Treatment lines were classified in combinations of chemotherapy and biologics. Logistic regression was used to predict receipt of treatment and subsequent treatment. Results: Among 3,266 beneficiaries diagnosed with mCC and initiated therapy, 1,440 progressed to 2nd line treatment and 274 progressed to 3rd line treatment. The strongest predictors of progressing to 2nd line treatment was surgery of the primary tumor site (OR: 2.42, 95% CI: 2.17-2.70) and regional/distal sites (OR: 1.32, 95% CI: 1.14-1.53) and marital status (OR: 1.64, 95% CI: 1.47-1.83). Older beneficiaries (80-84 years (OR: 0.31, 95% CI: 0.26-0.37) and > 85 years (OR: 0.10, 95%CI: 0.08-0.12)) and those with poor performance status indicators (walk aid (OR: 0.46, 95% CI: 0.26-0.82), wheelchair use (OR: 0.43, 95% CI: 0.29-0.64), and use of oxygen (OR: 0.54, 95% CI: 0.41-0.69)) were less likely to proceed to 2nd line treatment. Older age was the biggest predictor of not proceeding to third-line treatment (80-84 years (OR: 0.42, 95% CI: 0.28-0.61) & > 85 years (OR: 0.10, 95%CI: 0.05-0.19)). No variables were statistically significant in predicting receipt of third-line chemotherapy. Conclusions: Surgery of the primary tumor site and of regional/distal sites were the most significant clinical variables predicting whether or not elderly patients proceed to second-line chemotherapy. Sociodemographic variables also predicted receipt of second-line chemotherapy.