Use and impact of intermittent versus continuous systemic treatment strategies in metastatic colorectal cancer in routine practice

Abstract

BACKGROUND Randomized trials have shown that intermittent treatment may reduce toxicity without compromising survival in patients with metastatic colorectal cancer (mCRC). A population-based study examined patterns of use of chemotherapy-free intervals (CFIs) in routine practice in Ontario and their impact on survival and toxicity. METHODS Patients treated with first-line intravenous chemotherapy for mCRC in Ontario between 2007 and 2009 were identified from administrative data. A CFI was defined as more than 56 days between 2 chemotherapy doses. A propensity score analysis was used to compare the survival of patients with CFIs and patients without CFIs, stratified by the type of first-line treatment: irinotecan (IRI), irinotecan plus bevacizumab (IRI-B), and oxaliplatin (OX). Toxicity was estimated on the basis of the rate of emergency room visits and hospitalizations. RESULTS There were 1989 patients who started first-line chemotherapy for mCRC in Ontario between 2007 and 2009, and 489 (25%) had at least 1 CFI. The median time to the first CFI was 155 days (interquartile range, 82-217 days). There was no difference in survival for the propensity score-matched patients with or without CFIs in the IRI (hazard ratio [HR], 0.93; P=.70) and OX groups (HR, 0.73; P=.06). Survival was worse in the CFI group for patients treated with IRI-B (HR, 1.28; P=.03). Toxicity was lower for patients with at least 1 CFI (0.17 vs 0.25 acute visits per person-month of treatment, P=.007), although the magnitude varied with the treatment type. CONCLUSIONS Intermittent treatment strategies are being used in routine practice for patients with mCRC. The impact on survival and toxicity varies with the type of first-line chemotherapy. Cancer 2015;121:2791-2798.