Timing of postoperative chemotherapy and prognosis in neoadjuvant-treated gastric cancer patients: a multicenter real-world cohort study.

[BACKGROUND] The optimal time to chemotherapy (TTC) in locally advanced gastric cancer (LAGC) patients treated with neoadjuvant chemotherapy (NLAGC) remains unclear.

[METHODS] Consecutive 524 patients with NLAGC between Jan. 2010 and Dec. 2022 were identified. Patients were categorized into three groups: TTC < 6w, 6w ≤ TTC ≤ 8w, and TTC > 8w. Survival analysis was conducted using the Cox proportional hazards model to assess the impact of TTC on gastric cancer-specific mortality (GCSM) and all-cause mortality (ACM). Cumulative competing risk curves were employed to evaluate the incidence of competing events.

[RESULTS] Overall, 451 patients were included.Cumulative competing risk curves showed that the 3-year ACM and GCSM were significantly lower in the 6w ≤ TTC ≤ 8w group (ACM: 19.7% vs. 37.2% vs. 39.7%, GCSM: 19.7% vs. 35.2% vs. 38.8%) compared to the TTC < 6w and TTC > 8w groups. Compared to patients with 6w ≤ TTC ≤ 8w, those with TTC < 6w or >8w had an increased risk of GCSM (HR: 2.792 and HR: 2.343, respectively) and ACM (HR: 3.102 and HR: 2.719, respectively) after adjusting for confounders. Furthermore, 6w ≤ TTC ≤ 8w had later peak recurrence compared to TTC < 6w and TTC > 8w (Peak months: 9.7 4.3 3.1).

[CONCLUSION] A postoperative chemotherapy timing of 6-8 weeks was associated with better survival and delayed recurrence in NLAGC patients. These findings suggest that the 6-8 week time-window should be a key timeframe for personalized postoperative adjuvant chemotherapy decisions.