3.1. Comparisons of overall patient characteristics between groups
Table 1 shows the comparison of characteristics between Group C and Group N in the SEER database. The results showed that the groups were significantly different according to Gender, Age, LN dissection, Size, and Histology (P < 0.05). The two groups did not significantly differ in AJCC staging, intestinal type, primary site, gastrectomy type or tumor grade (P > 0.05). Supplemental Table 1 shows the characteristics of patients with AC and non-AC in the FJUUH dataset. The two groups of patients exhibited significant differences in Age (P = 0.003) but not Gender, body mass index (BMI), American Society of Anesthesiologists (ASA) score, AJCC staging, Histology, Anastomosis method, Esophagus invasion, Duodenum invasion, Operation time, Bleeding loss, LN dissection number, Size, or Primary site (P > 0.05). Supplemental Table 2 shows the comparison of characteristics of patients with AC and non-AC in the IMIGASTRIC center dataset. There were significant differences between the groups in ASA score, Approach, and Operation time (P < 0.05) but not Gender, Age, BMI, AJCC staging, Histology, Anastomosis method, Bleeding Loss, LN dissection number, Size, or Primary Site (P > 0.05).
3.2. Five-year OS of patients with AC in the SEER database
Supplemental Table 3 shows the results of univariate and multivariate Cox regression analyses, which were used to predict OS in patients with AC. After stepwise backward variable selection, only patients with Age > 65 years old , T1N2M0, LN dissection number ≤ 15, Size ≥ 20 mm, and nonadenocarcinoma remained in the final model (P < 0.05). The final model served as the basis for the multivariate nomogram (Figure 1).
3.3. Division of patients with AC into groups according to differences in degree of benefit
In this study, the optimal cut-off value for nomogram-predicted 5-year OS was 188 according to the recursive partitioning analysis. Patients with AC were divided into two groups, with those with points ≤188 regarded as high-benefit patients and those with points > 188 regarded as low-benefit patients. In addition, according to the nomogram, the low-benefit patients had some of the following features: (1) Age > 65 years old, (2) LN dissection ≤ 15, (3) Size ≥ 20 mm, (4) and nonadenocarcinoma. T1N2M0 patients with more than one of these four pathological characteristics were regarded as low-benefit patients, while T3N0M0 patients with more than three of these four pathologies were considered low-benefit patients.
3.4. Comparison of OS between patients with different degrees of benefit and non-adjuvant chemotherapy
In the analyses of the SEER database, the FJUUH center dataset and the IMIGASTRIC center dataset, OS was consistently better in patients with AC than in those without AC (Log-rank = 0.0001, 0.012, and 0.042, respectively) (Supplemental Figure 1-3). We next compared the 5-year OS of patients in the three centers among those with a high benefit from AC, a low benefit from AC and non-AC. The results showed that in the SEER database and FJUUH datasets, OS was significantly better in the high-benefit patients than in low-benefit patients (Log-rank = 0.001 and 0.004, respectively) and the non-AC patients (Log-rank = 0.000 and 0.003) (Figure 2 and Figure 3). However, in the IMIGASTRIC dataset, OS was similar between the high-benefit and low-benefit patients (Log-rank = 0.060) (Figure 4). Furthermore, there was no significant difference in OS between the low-benefit patients and non-AC patients at any of the three centers (Log-rank = 0.154, 0.470 and 0.419) (Figure 2-4).
3.5. The decision curve
Finally, we established a decision curve from the nomogram (Supplemental Figure 4). The results showed that the maximum benefit was obtained when the decision threshold was 0-92%, indicating that in patients with pathological stage T3N0M0 and T1N2M0, AC should be perform in patients with a score ≤ 188. Using this method, a better curative effect will be obtained than if all T3N0M0 and T1N2M0 patients do or do not undergo AC.