Impact of RAS testing on treatment duration among patients with metastatic colorectal cancer (mCRC).

Abstract

773 Background: Current clinical guidelines recommend that all patients with mCRC have tumor tissue genotyped for RAS mutations. Tumor RAS testing enables the widest range of treatment options, with potential impact on patient outcomes. The aim of this study was to estimate the impact of RAS testing on the duration of treatment, across multiple lines of chemotherapy in mCRC. Methods: Adults with a diagnosis of mCRC (ICD-9 codes 153.x, 154.0x, or 154.1x and 197.x–198.x) were identified from a database of US public and private insurance claims (129 million covered lives) from 2012–2014. Time to treatment discontinuation, overall and by line of chemotherapy, was compared through univariate analysis between patients who were tested for RAS mutations (identified by CPT codes) to those who were not tested. Multivariate Cox proportional hazard regression model was used to estimate the risk of discontinuation attributable to prior RAS testing (i.e., hazard ratio [HR]), adjusting for patient characteristics. Results: We identified 4,527 mCRC patients (mean age at diagnosis, 61.2 years; 54% male), 39% (n = 1,787) of whom had a claim for RAS testing during the study period. Patients tested for RAS mutations stayed on treatment significantly longer in first-line (1LD), second-line (2LD), and overall treatment (OTD) vs those who were not tested for RAS mutations (1LD: median, 245 days [95% confidence interval–CI: 232–251] vs 196 days [95% CI: 189–205]; 2LD: median, 189 days [95% CI: 168–203] vs 147 days [95% CI: 133–161]; OTD: median, 903 days [95% CI: 815–1,040] vs 305 days [95% CI: 281–337]; all P < 0.01). Adjusting for patient characteristics, RAS testing significantly reduced the risk of discontinuation in 1LD, 2LD, and OTD (HRs: 0.83 [95% CI: 0.76–0.90], 0.80 [95% CI: 0.71–0.91], and 0.32 [95% CI: 0.27–0.37], respectively; all P< 0.01). Conclusions: These observational data show that RAS testing is associated with significantly greater time on treatment for mCRC patients compared to not testing, suggesting that patients under the care of physicians who decide to test for RAS mutations, regardless of test result, are on therapy for a longer period of time than untested patients.