Effect of lymph node dissection numbers after conversion immunochemotherapy on the survival of gastric cancer patients: a multi-center retrospective study.

OBJECTIVE

To investigate the influence of lymph node dissection on the prognosis of unresectable locally advanced gastric cancer (LAGC) after conversion immunochemotherapy (CICT).

METHODS

A total of 287 patients, including 227 from Nanjing Drum Tower Hospital and an external validation cohort of 60 patients (15 from Peking Union Medical College Hospital, 20 from Beijing Friendship Hospital, and 25 from PLA General Hospital) with pathologically diagnosed unresectable primary LAGC (cT3~4N+) underwent radical gastrectomy after multidisciplinary evaluation conversion immunochemotherapy (CICT) were enrolled, and their clinical data were collected. According to the pathological data of patients' baseline data set, a clinical prediction model of patients' overall survival (OS) and progression-free survival (PFS) was established, and based on COX regression model, the critical value of the number of lymph node dissection was determined by restricted cubic spline (RCS) analysis.

RESULTS

Univariate and multivariate COX regression analysis showed that lymph node metastasis (ypN+) was an independent risk factor for OS (P = 0.030) and PFS (P = 0.002). According to the results of COX regression analysis, the prediction model was established. RCS curve showed that the critical number of lymph node dissection was 21 and 28. Patients with 21-28 lymph node dissection had the best OS and PFS. Compared with the patients with 21-28 lymph nodes dissection, the patients with less than 21 lymph nodes dissection had worse OS (P<0.001) and PFS (P = 0.002). Those with more than 28 lymph nodes isolated had worse OS(P = 0.043) and PFS (P = 0.027). The PFS of patients with more than 28 lymph nodes dissection was better than the patients with less than 21lymph nodes dissection (P = 0.031). Although the difference was not statistically significant, the total OS of patients with more than 28 lymph nodes dissection was still higher than that of patients with less than 21 lymph nodes dissection (P = 0.077).

CONCLUSION

Among patients after CICT, lymph node metastasis (ypN+) is an independent risk factor for the prognosis of patients. The survival benefit of patients with less than 21 lymph node dissection is significantly reduced, while those with more than 28 lymph node dissection are less than 21-28 lymph node dissection.