Ten studies (n=15,422 participants, sample size 179 to 6,059) were included in the review. There were nine cohort studies and one secondary analysis from a randomised controlled trial. Individual quality assessment results were not presented. All 10 studies reported on overall survival; six studies (n=12,522) also reported on disease-free survival.
Statistically significant decreases in overall survival (HR 1.14, 95% CI 1.10 to 1.17) and disease-free survival (HR 1.14, 95% CI 1.10 to 1.18) were associated with increased time interval (per four weeks of waiting time) between surgery and initiation of adjuvant chemotherapy. There was no statistically significant heterogeneity and no evidence of publication bias.
Sensitivity analysis did not materially alter the main findings. A separate analysis of three studies that reported cancer-specific survival was similar to overall survival (HR 1.15, 95% CI 1.10 to 1.19). Other survival data (such as five-year overall survival) were reported.