Clinical outcomes of conversion surgery following immune checkpoint inhibitors and chemotherapy in stage IV gastric cancer

Background: The clinical benefit of conversion surgery following immunochemotherapy in patients with stage IV gastric cancer (GC) remains uncertain. This study aims to clarify the clinical outcomes of conversion surgery for such patients. Methods: This retrospective cohort study enroled consecutive patients with stage IV GC treated with a combination of immune checkpoint inhibitors and chemotherapy and/or anti-human epidermal growth factor receptor-2 targeted therapy as first-line therapy. Cumulative survival curves were estimated using Kaplan–Meier method. Logistic regression and Cox regression analyses were conducted to identify factors associated with conversion surgery and survival, respectively. Results: Among the 136 patients included in the study. The disease control rate was 72.1% (98/136), with objective response rate in 58.8% (80/136) and complete response rate in 5.9% (8/136). Among 98 patients with disease control, 56 patients underwent palliative immunochemotherapy with median progression-free survival (PFS) and overall survival at 9.2 and 16.2 months, respectively; the remaining 42 patients underwent conversion surgery, yielding an unreached median PFS over a 19.0-month median follow-up, accompanied by 1-year overall survival and PFS rates of 96.6% and 89.1%, respectively. The R0 resection rate reached 90.5% (38/42). 7 out of 42 patients achieved pathological complete response, of whom three patients demonstrated human epidermal growth factor receptor-2 positivity. No serious complications leading to death were observed during the perioperative period. Multivariate analysis indicated that programmed death ligand 1 combined positive score greater than or equal to 5 (odds ratio, 0.22; 95% CI, 0.08–0.57; P =0.002) favored successful conversion surgery, while signet ring cell carcinoma (hazard ratio, 6.29; 95% CI, 1.56–25.36; P =0.010) was the poor prognostic factor associated with survival in patients who underwent conversion surgery. Conclusions: Conversion surgery holds the potential for significant survival benefits in stage IV GC patients who have achieved a favourable clinical response to immunochemotherapy. Individuals with signet ring cell carcinoma may experience increased post-conversion surgery recurrence.