Objective To investigate the postoperative recurrence-free survival (RFS) and influencing factors of gastrointestinal stromal tumors (GISTs) patients with and without KIT gene exon 11 codon 557 and/or 558 deletion mutations (referred to as 557/558 deletion mutations).

Methods The propensity score matching and retrospective cohort study was conducted. The clinico-pathological data of 337 patients with GISTs who underwent operation at Northern Jiangsu People′s Hospital from January 2006 to December 2022 were collected. There were 198 males and 139 females, aged (59±10)years. Of 337 patients with primary GISTs, 97 cases with KIT gene 557/558 deletion mutations were allocated into 557/558del group, and the rest 240 cases without KIT gene 557/558 deletion mutations were allocated into non-557/558del group. Observation indi-cators: (1) propen-sity score matching and comparison of clinicopathological data of patients between the two groups after matching; (2) follow-up and RFS; (3) analysis of influencing factors for RFS of patients. Compari-son of count data between groups was conducted using the chi-square test. Com-parison of ordinal data between groups was conducted using the non parametric rank sum test. Kaplan-Meier method was used to calculate survival rate and plot survival curve, and Log-rank test was used for survival analysis. Univariate and multivariate analyses were conducted using the Cox proportional hazard model. Propensity score matching was done by the 1∶1 nearest neighbor matching method. The caliper value was set as 0.02.

Results (1) Propensity score matching and comparison of clinicopatholo-gical data of patients between the two groups after matching. Of 337 patients, 168 cases were succe-ssfully matched, including 84 cases in the 557/558del group and 84 cases in the non-557/558del group.After propensity score matching, the confounding bias of mitotic index, modified National Institutes of Health risk classification, Armed Forces Institute of Pathology risk classifica-tion before matching were eliminated between the two groups, ensuring comparability. (2) Follow-up and RFS. All 337 patients were followed up for 35(range 2‒120)months. There were 55 cases of postoperative recurrence or metastasis. After propensity score matching, the 1-, 2-, and 5-year RFS rates in the 557/558 del group were 96.34% 95% confidence interval (CI) as 89.08%-98.80%, 88.28%(95%CI as 78.63%-93.74%), and 70.54%(95%CI as 55.26%-81.44%), respectively. For the non-557/558 del group, the corresponding rates were 92.78%(95%CI as 84.64%-96.69%), 87.44%(95%CI as 77.86%- 93.06%), and 84.00%(95%CI as 73.33%-90.67%). There was no significant difference in RFS between the two groups (χ²=2.291, P > 0.05).(3) Analysis of influencing factors for RFS of patients. Results of multivariate analysis showed that tumor location, tumor diameter, mitotic index, and muta-tion subtype were independent factors influencing postoperative RFS of GISTs patients before pro-pensity score matching (hazard ratio=3.262, 1.110, 3.041, 7.082, 2.945, 95%CI as 1.874-5.680, 1.039-1.186, 1.681-5.503, 3.304-15.180, 1.681-5.158, P < 0.05).

Conclusions There is no significant difference in postoperative RFS of GISTs patients with and without KIT gene 557/558 deletion muta-tions. Tumor location, tumor diameter, mitotic index and mutation subtype are independent factors influencing postoperative RFS in GISTs patients.