Effect of metastatic lymph node ratio on the prognosis of adjuvant radiotherapy for stage-Ⅲ gastric cancer patients / 中华放射医学与防护杂志

ABSTRACT

Objective:To explore the effect of metastatic lymph node ratio (MLR) on the prognosis of adjuvant radiotherapy for stage-Ⅲ gastric cancer patients with no more than 15 lymph nodes dissection.Methods:According to the inclusion and exclusion criteria, a total of 590 patients diagnosed with stage-Ⅲ gastric cancer (excluding adenocarcinoma of esophagogastric junction) were included in this study from the SEER database between 2010 and 2016. No more than 15 lymph nodes were examined in all patients. Among them, 291 patients received surgery combined with adjuvant chemotherapy (surgery + chemotherapy group), and 299 patients received surgery combined with adjuvant radiochemotherapy (surgery + radiochemotherapy group). These two groups were treated with 1∶1 propensity score matching (PSM). We retrospectively analyzed the effect of MLR on prognosis of stage-Ⅲ gastric cancer patients with no more than 15 lymph nodes dissection, and evaluated the significance of postoperative adjuvant radiotherapy among patients with different MLR.Results:According to the analysis result of area under curve (ROC), 0.5 was defined as the best cut-off point of MLR. In the two groups of patients with stage-Ⅲ gastric cancer included in the study, the median survival time was 23 months in the surgery + radiochemotherapy group, and the 1 -, 3 -, and 5-year overall survival (OS) ratio were 77.1%, 33.2% and 22.8%, respectively. The median survival time was 21 months in the surgery + chemotherapy group, and the 1 -, 3 -, and 5-year OS ratio were 72.2%, 33.6% and 23.1%, respectively. There was no statistically significant difference between the two groups in OS. The result of subgroup analysis showed that there was no statistically significant difference in OS between the surgery + radiochemotherapy group and the surgery + chemotherapy group among patients with MLR≤0.5, while OS of the surgery + radiochemotherapy group was significantly better than the surgery + chemotherapy group among patients with MLR>0.5( χ2=8.542, P < 0.05). Multivariate Cox regression analysis showed that race, T stage, N stage, MLR and adjuvant radiotherapy were the important factors affecting OS of stage-Ⅲ gastric cancer patients with no more than 15 lymph nodes dissection( Wald=8.544, 7.547, 10.925, 18.047, 10.715, P < 0.05). After PSM, there was no statistically significant difference in OS between the two groups. The result of subgroup analysis showed that there was no statistically significant difference in OS between the surgery + radiochemotherapy group and the surgery + chemotherapy group among patients with MLR≤0.5, while OS of the surgery + radiochemotherapy group was significantly better than the surgery + chemotherapy group among patients with MLR>0.5( χ2=6.944, P < 0.05). Multivariate Cox regression analysis showed that race, T stage, N stage, MLR and adjuvant radiotherapy were the important factors affecting OS of stage-Ⅲ gastric cancer patients with no more than 15 lymph nodes dissection ( Wald=7.154, 8.023, 7.744, 17.016, 4.149, P < 0.05). The result of prognosis analysis of two groups before and after PSM were consistent. Conclusions:MLR is an important prognostic factor for stage-Ⅲ gastric cancer patients with no more than 15 lymph nodes dissection. The OS of patients with MLR ≤ 0.5 can′t benefit from postoperative adjuvant radiotherapy, while patients with MLR > 0.5 should be advised to receive postoperative adjuvant radiotherapy to improve the prognosis.