Real-World Effect of Maintenance and Intermittent Chemotherapy on Survival in Metastatic Colorectal Cancer

Improved outcomes in metastatic colorectal cancer are allowing patients to consider periods of reduced-intensity chemotherapy, however real-world use of these modifications is poorly described. In this population-based cohort, 39% of patients used either intermittent or maintenance chemotherapy during treatment and modifications were associated with improved outcomes, suggesting physicians can appropriately select patients who are safe to undergo treatment modifications. With improved survival and longer duration of treatment, clinicians managing metastatic colorectal cancer (mCRC) increasingly consider intermittent (IC) or maintenance chemotherapy (MC), but the effect of these treatment modifications on real-world outcomes is unclear. Using a population-based cohort of mCRC patients who received combination chemotherapy, we aimed to describe the use of IC/MC and their effect on overall survival (OS). Among 617 patients, 120 (19%) had periods of IC, 67 (11%) had periods of MC, and 53 (9%) had periods of both. Most (85.5%) modifications occurred in the first-line setting. The receipt of IC (median OS [mOS], 37 vs. 21 months; P < .0001) or MC (mOS, 36 vs. 24 months; P = .0015) was associated with improved mOS compared with continuous combination therapy. In multivariate analysis adjusting for age, sex, and regimen used at the time of treatment modification, IC (hazard ratio [HR], 0.52; 95% confidence interval [CI], 0.42-0.65; P < .0001), MC (HR, 0.71; 95% CI, 0.58-0.88; P = .002), and the combination (HR, 0.45; 95% CI, 0.33-0.63; P < .0001) were all associated with improved mOS. Among patients receiving MC, individuals with (HR, 0.69; 95% CI, 0.53-0.90; P = .005) and without (HR, 0.74; 95% CI, 0.55-1.00; P = .048) re-escalation to their original cytotoxic regimen had improved mOS compared with continuous therapy. The use of IC was associated with an improved OS compared with MC (HR, 0.65; 95% CI, 0.47-0.90; P = .009). In patients with mCRC, IC and MC are reasonable options to maintain quality of life and do not appear to negatively affect OS in carefully selected patients.