Abstract
IMPORTANCE: Phase 3 trials for patients with metastatic colorectal cancer (mCRC) have been conducted with varying designs and often with surrogate end points for overall survival (OS). OBJECTIVES: To critically examine the factors associated with clinically relevant improvement in OS (defined as ≥2 months) in these trials and to evaluate their association with outcomes reflected in Surveillance, Epidemiology, and End Results (SEER) registry data. EVIDENCE REVIEW: Medline, EMBASE, Cochrane, Web of Science, ClinicalTrials.gov, EU Clinical Trials Register, and the International Clinical Trials Registry Platform were searched for phase 3 trials of systemic therapy for patients with mCRC by decade (1986-1996, 1997-2006, and 2007-2016), excluding early or pilot studies, studies that did not involve an anticancer drug, studies on cancer screening and prevention, reports of pooled data from multiple trials, and studies with nonpharmaceutical approaches. The association of drug development with OS outside the clinical trial setting was evaluated using data from the SEER registry, including adult patients with a primary cancer site in the colon or rectum, including adenocarcinoma, mucinous adenocarcinoma, or signet ring cell carcinoma; a distant stage; and receipt of chemotherapy as first-line therapy. Kaplan-Meier curves and log-rank tests were used to assess OS. FINDINGS: The literature search identified 150 phase III clinical trials with 77 494 total enrollments, and 67 126 patients with mCRC were identified from the SEER database. Significant increases in survival were noted over time, best reflected in the experimental arm of first-line therapy (OS increased by 5.7 months per 10 years; 95% CI, 4.7-6.6 months; progression-free survival increased by 1.4 months per 10 years; 95% CI, 0.7-2.1 months). Although 69 of 148 trials (46.6%) met their predefined primary end point (including 20 of 44 trials [45.5%] with OS as the primary end point), only 35 of 132 trials (26.5%) resulted in improvement in OS by 2 months or more (including 13 of 42 trials [31.0%] with OS as the primary end point). Multivariable logistic regression showed that third-line therapies or later (odds ratio, 0.57; 95% CI, 0.51-0.63) and funding by pharmaceutical companies (odds ratio, 0.57; 95% CI, 0.54-0.60) were less often associated with improvement in OS. Furthermore, there was a decrease in the novelty of targets and agents over time, with trials that evaluated regimens composed entirely of previously approved drugs for mCRC increasing from 28% to 50%. Data from the SEER database showed that median OS increased from 12 months (95% CI, 12-13 months) (1986-1996) to 21 months (95% CI, 21-22 months) (2007-2015) (P < .001), but the 5-year OS continued to be low at 12.2% in 2011. CONCLUSIONS AND RELEVANCE: In this systematic review, OS for patients with mCRC appeared to improve significantly in trials, translating into meaningful benefits outside the clinical trial setting; however, these advances, although significant cumulatively, are largely incremental individually. These data should be a call to aim for larger gains from future trials with novel drugs, building on the increasing understanding of the biology of mCRC and sophisticated translational research tools.