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.