2-4 weeks is the optimal time to operate on colorectal liver metastasis after neoadjuvant chemotherapy.

Neoadjuvant chemotherapy (NAC) is generally accepted for treatment of liver metastasis of colorectal cancer (CRLM), but what is a reasonable interval between the latest NAC and surgery is still unknown. The aim of the current study was to investigate the proper timing of surgery after NAC. Subjects were 141 patients with CRLM who underwent NAC and then surgery were retrospectively identified from 2008 to 2020. They were divided into a short interval group (SIG, ≤ 4 weeks) and long interval group (LIG, > 4 weeks) using the software X-tile. The SIG was subclassified group into 3 time periods (1-2 weeks, 2-3 weeks, and 3-4 weeks) to assess the incidence of complications. Patients in the SIG were more likely to have significantly better recurrence-free survival (RFS) (3-year RFS of 47.4% vs. 20.5%, P = 0.043) and no difference in overall survival (OS) (3-year OS 76.1% vs. 79.9%, P = 0.635). The postoperative complication rate was 23.5% in the SIG and 14.0% in the LIG (P = 0.198). The postoperative complication rate in the 1-2 weeks subgroup was marginally higher than that in the > 4 weeks subgroup (35% vs. 14.3% P = 0.055). Multivariate analysis revealed that chemotherapy-free intervals of 1-2 weeks were an independent predictor of increased postoperative complications (OR = 0.263, 95% CI 0.7-0.985 P = 0.048). Patients who underwent surgery within 4 weeks of NAC had better RFS. In addition, 1-2 weeks was an independent factor influencing the development of more complications. For patients with CRLM, performing surgery within 2-4weeks of NAC was feasible and safe, and it did not increase the incidence of postoperative complications but it did prolong RFS.