Oncology · Medical Literature
The Impact of Early Versus Delayed Chemotherapy on Survival in Patients with Colorectal Cancer after Surgery: A Systematic Review and Meta-Analysis.
Abstract
This study systematically evaluates the impact of the initiation time of postoperative chemotherapy on overall survival (OS) in patients with colorectal cancer, providing evidence to guide clinical decisions on chemotherapy timing. Following PRISMA and MOOSE guidelines, PubMed, Embase, Web of Science, and the Cochrane Library were systematically searched up to February 2025. Cohort studies comparing early versus delayed postoperative chemotherapy were included. Two researchers independently performed literature screening, data extraction, and quality assessment. Review Manager 5.3 was used, with hazard ratios (HRs) and 95% confidence intervals (CIs) as effect measures. Random- or fixed-effects models were applied based on heterogeneity, and subgroup and sensitivity analyses were conducted. Eleven studies involving 72,873 patients were included. Pooled results showed that delayed chemotherapy significantly increased the risk of death (HR = 1.32, 95% CI: 1.20-1.45, P 8 weeks (HR = 1.47, 95% CI: 1.14-1.91, P = 0.003). Delayed postoperative chemotherapy markedly increases mortality risk. Initiating adjuvant chemotherapy within 8 weeks after surgery is recommended to achieve optimal survival benefits.
Clinical relevance
Optimal timing of adjuvant chemotherapy initiation after colorectal cancer (CRC) resection remains insufficiently defined in current guidelines, creating practice variability that may adversely affect patient outcomes. This meta-analysis addresses that gap by pooling data from 72,873 patients across 11 cohort studies, representing one of the largest such analyses to date focused specifically on postoperative chemotherapy timing in CRC. Given that CRC is among the most prevalent and lethal malignancies worldwide, establishing an evidence-based window for adjuvant chemotherapy initiation has direct and immediate clinical implications for surgical oncology and medical oncology practice.
Key findings
1. Delayed postoperative chemotherapy was associated with a significantly increased risk of death compared to early initiation: pooled HR = 1.32 (95% CI: 1.20–1.45, P < 0.00001), representing a 32% relative increase in mortality risk. 2. High interstudy heterogeneity was observed (I² = 88%), reflecting variability in study populations, chemotherapy regimens, and definitions of 'delayed' initiation; sensitivity analyses confirmed the robustness of the primary findings despite this heterogeneity. 3. Subgroup analysis using an 8-week cutoff demonstrated that patients initiating chemotherapy more than 8 weeks postoperatively had significantly worse overall survival than those starting within ≤8 weeks: HR = 1.47 (95% CI: 1.14–1.91, P = 0.003), indicating a 47% relative increase in mortality risk with delay beyond 8 weeks. 4. The meta-analysis adhered to PRISMA and MOOSE reporting guidelines, with two independent researchers performing screening, data extraction, and quality assessment, supporting methodological rigor. 5. The study included 11 cohort studies with a combined sample of 72,873 patients, providing substantial statistical power for effect estimation. 6. Both random- and fixed-effects models were applied based on heterogeneity assessment, and effect measures were reported as hazard ratios with 95% confidence intervals, consistent with standard meta-analytic methodology for time-to-event outcomes.
Practice implications
Clinicians should prioritize initiating adjuvant chemotherapy within 8 weeks of curative-intent colorectal cancer surgery; delays beyond this threshold are associated with a 47% relative increase in mortality risk (HR = 1.47, 95% CI: 1.14–1.91) and should be avoided whenever clinically feasible. Multidisciplinary care coordination—including early oncology consultation, proactive management of postoperative complications, and streamlined pathology and staging workflows—should be embedded into institutional protocols to safeguard timely chemotherapy initiation, particularly for stage II and III CRC patients. Where surgical morbidity threatens to delay chemotherapy beyond 8 weeks, oncology teams should weigh the risk-benefit of earlier initiation against the patient's recovery status, and systems-level interventions should be considered to reduce modifiable delays in high-risk patient subgroups.