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 1,989 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.