Study population
From November 2009 to December 2018, 797 patients were enrolled in our research. A total of 722 (90.6%) gastric adenocarcinoma cases (non-HAS) and 75 (9.4%) HAS cases were detected by histological morphology and immunohistochemistry. However, 11 non-HAS and 2 HAS patients hand distant metastases (M1). To reduce bias, these patients were excluded from this evaluation. Through one-to-one nearest-neighbour matching with a 0.02 caliper width, 144 patients were included for analysis, with 72 HAS and non-HAS patients each. Through one-to-two nearest-neighbour matching with a 0.05 caliper width, 165 patients were included in our study, with 110 non-HAS patients and 55 HAS patients. (Fig. 1)
Clinicopathological characteristics
For the 797 patients, the two groups (HAS and non-HAS) were consistent in terms of sex, age, tumor location, surgery type, vascular invasion, and N (lymph node metastasis) and M stage (distant metastasis). Nevertheless, the two groups were differentially distributed in terms of T stage, EGFR, KI-67, CEA, CA199, HER-2 and neoadjuvant chemotherapy. One-to-one and one-to-two nearest-neighbour matching were used to generate 144 and 165 patients from the two groups, respectively. They showed no significant bias in clinicopathological characteristics. (Additionalfile1: Table1)
Survival among all patients and propensity-matched pairs
In our analysis, we found that OS was not significantly different between the HAS group and the non-HAS group (Fig. 2). The median follow-up time of the pre-PSM cohort was 22.0 months (rang= 0 to 97months). The median follow-up time was 15.0 months (rang=0 to 97 months) after 1:1 PSM. The median follow-up time was 21.0 months(range=0 to 97 months)after 1:2 PSM. Among the 784 patients (13 patients with distant metastasis were excluded from 797 patients) in our study, the 1-, 2-, and 3-year survival rates of non-HAS patients were 92.6%, 81.1%, and 75.0%, and those of HAS patients were 87.9%, 86.2%, and 82.6%, respectively. Among the one-to-one nearest-neighbour matched pairs of patients, the 1-, 2-, and 3-year survival rates of non-HAS patients were 94.4%, 86.5%, and 82.3%, and those of HAS patients were 92.9%, 86.3% and 84.5%, respectively. Among one-to-two nearest-neighbour matched pairs of patients, the 1-, 2-, and 3-year survival rates of non-HAS patients were 98.1%, 98.1%, and 96.9%, and those of HAS patients were 90.3%, 83.9% and 79.9%, respectively.
Risk factors for prognosis
Among the 784 patients, univariate analysis showed that the tumour location, surgery type, vascular invasion, T and N stage, the levels of CEA and CA19-9, EGFR expression and neoadjuvant chemotherapy were significantly associated with OS. Among the one-to-one nearest-neighbour matched pairs of patients, T and M stage, EGFR expression and neoadjuvant chemotherapy were found to be significantly related to OS. Among the one-to-two propensity-matched pairs of patients, T and M stage, level of CEA and EGFR expression were significantly associated with OS (Table 2).
Among the 784 patients, multivariate analysis identified prognostic factors including T and N stage, EGFR and neoadjuvant chemotherapy. There was no statistical difference of OS between HAS and non-HAS by using multivariable Cox regression models given the following covariance: age, tumor location, surgery type, vascular invasion, T and N stage, the level of CEA and CA199, EGFR and neoadjuvant chemotherapy. (P=0.619) (Table 3a). Among the one-to-one nearest-neighbour matched pairs of patients, the univariate analysis identified some factors significantly related to OS, including the T stage, M stage, the level of CEA, EGFR and neoadjuvant chemotherapy. There was no statistical difference of OS between HAS and non-HAS by using multivariable Cox regression models given the following covariance: age, vascular invasion, TNM stage, the level of CEA and CA199, EGFR and neoadjuvant chemotherapy. (p=0.841) (Table 3b). Among the one-to-two nearest-neighbour matched pairs of patients, M stage and the level of CEA associated with OS. There was no statistical difference of OS between HAS and non-HAS by using multivariable Cox regression models given the following covariates: age, vascular invasion, TNM stage, the level of CEA and CA199, EGFR and neoadjuvant chemotherapy. (p=0.098) (Table 3c).