The impact of comorbidity on costs and effects of second-line treatment among elderly metastatic colon cancer patients.

Abstract

536 Background: The Charleston Co-morbidity Index (CCI) was developed as in hospital mortality indicatory and subsequently has been used to both predict and adjust survival differences in cancer patients. We therefore sought to examine how the incremental cost effectiveness of treating elderly metastatic colon cancer (mCC) patients with second-line treatment (Tx2) will vary based upon their baseline CCI. Methods: We identified 2,897 elderly (age 66+) mCC patients who received NCCN recommended first-line treatment (Tx1) between 2003 and 2009 in the SEER-Medicare dataset. Approximately 6% and 1% of patients with missing CCI and outlier costs, respectively, were excluded. We categorized patients by their CCI for 12 months prior to diagnosis into three categories: low (CCI = 0), medium (CCI = 1) and high (CCI = 2+). We calculated 5-years cost-effectiveness of Tx2. Patients enrolled in HMOs, lost part A and/or B, and died of causes other than colon cancer are censored. Costs are inflation adjusted to January 2009 dollars using U.S. Medical Price Index (MPI). We adjusted for censoring using Inverse Probability Weighting (IPW) method and selection bias on observables using Propensity Score Bin Bootstrapping method. Results: Among patients who received Tx1, 56% (n = 1,285) proceeded to receive Tx2. Of those who received Tx2, 67% (n = 864), 23% (n = 289), and 10% (n = 132) have low, medium and high comorbidities, respectively. Compared to those who do not received Tx2, patients who received Tx2 with low, medium, and high baseline comorbidities live 18 (se = 4), 253 (se = 4), and 183 (se = 3) days longer and incur added costs of $66,693 (se = $675), $80,217 (se = $723), and $49,610 (se = $1,136), respectively. The median Incremental Cost-Effectiveness Ratios (ICERs) of Tx2 for patients with low, medium, and high comorbidity are $80,049, $114,693, and $151,627, respectively. Conclusions: Survival benefits from receiving Tx2 vary from an average of 18 days to 253 days and added costs from $49,610 to $80,217 depending on baseline comorbidity levels. The median ICERs associated with Tx2 increase as baseline comorbidity level of patients increase.