Prognostic value of a modified pathological staging system for gastric cancer based on the number of retrieved lymph nodes and metastatic lymph node ratio raw data

Clinical data from the US Surveillance, Epidemiology, and End Results (SEER) Program from 2010-2015 (https://seer.cancer.gov/) was extracted and analyzed as training set, data from 2016-2017 was adopted as internal validation set. Data from The Cancer Genome Atlas Program (TCGA) (https://portal.gdc.cancer.gov/) and prognosis data from Gastrointestinal surgery Department, Third Affiliated Hospital of Sun Yat-sen University were applied as external validation sets.

Screening criteria for gastric cancer cases were as follow: exclusion of cases with only autopsy or death certificate, cases where initial tumor location was not stomach, patients with stage 0 and stage IV, cases without radical surgery, non-adenocarcinoma cases, death cases within one month after operation, and cases with unknown lymph node information and AJCC TNM stage.

The study analyzed various factors such as age of diagnosis (<50 years, 50-69 years, >69 years), gender, race (white, black, other), AJCC T stage (T1-T4b), AJCC TNM stage (I-III), primary tumor location (stomach body, antrum/pylorus, cardia/fundus, greater gastric recurve, lesser gastric recurve, overlapping area, NOS), Clinical features such as tumor size (≥5cm,<5cm, unknown), tumor grade (I-IV), chemotherapy, radiotherapy, number of lymph nodes retrieved and number of metastases, and lymph node positive rate. The populations of American Indian/Alaskan and Asian/Pacific Islander were classified as "other" due to small sample sizes. Tumor grade was also analyzed, with grades I-IV representing highly differentiated, moderately differentiated, poorly differentiated, and signed-ring cell carcinoma, respectively. Overall survival (OS) is the time from cancer diagnosis to death from any cause, while disease-specific survival (DSS) is the time from cancer diagnosis to death specifically due to the disease.

本研究提取并分析美国监测、流行病学与最终结果（Surveillance, Epidemiology, and End Results, SEER）项目2010-2015年的临床数据（https://seer.cancer.gov/）作为训练集，将该项目2016-2017年的数据作为内部验证集。同时采用美国癌症基因组图谱（The Cancer Genome Atlas Program, TCGA）项目数据（https://portal.gdc.cancer.gov/）与中山大学附属第三医院胃肠外科的预后数据作为外部验证集。

胃癌病例的筛选标准如下：排除仅具备尸检报告或死亡证明的病例、初始肿瘤部位非胃部的病例、0期及IV期患者、未接受根治性手术的病例、非腺癌病例、术后1个月内死亡的病例，以及淋巴结信息与AJCC TNM分期未知的病例。

本研究分析了多项临床与病理因素，包括诊断年龄（分为<50岁、50~69岁、>69岁三组）、性别、种族（分为白人、黑人、其他三类）、AJCC T分期（T1~T4b）、AJCC TNM分期（I~III期）、原发肿瘤部位（包括胃体、胃窦/幽门、贲门/胃底、胃大弯、胃小弯、重叠区域、未特指（NOS））；临床特征包括肿瘤大小（分为≥5cm、<5cm、未知三类）、肿瘤分级（I~IV级）、化疗情况、放疗情况、送检淋巴结数目与转移淋巴结数目，以及淋巴结阳性率。由于样本量较小，将美洲印第安人/阿拉斯加原住民以及亚洲/太平洋岛民群体归类为“其他”类别。本研究同时对肿瘤分级进行了细分：I~IV级分别对应高分化、中分化、低分化与印戒细胞癌。总生存期（Overall Survival, OS）指从癌症确诊至因任何原因死亡的时间，而疾病特异性生存期（Disease-Specific Survival, DSS）指从癌症确诊至因该疾病特异性死亡的时间。