Terashima M, Sano T, Mizusawa J, Umemura K, Tokunaga M, Omori T, Cho H, Hasegawa Y, Akiyama Y, Tsujimoto H, Kawashima Y, Kawachi Y, Lee SW, Kano K, Hasegawa H, Boku N, Yoshikawa T, and Sasako M
Background: Indications for adjuvant chemotherapy for advanced gastric cancer are determined based on the pathological diagnosis. However, macroscopic diagnoses have been reported as predictors of peritoneal recurrence and survival. This study investigated the predictability of peritoneal recurrence and survival based on macroscopically (sT) and pathologically (pT) diagnosed serosal invasion to identify more sensitive predictors of peritoneal recurrence., Methods: This study included 396 patients who underwent R0 resection without adjuvant chemotherapy with S-1 in the JCOG0110 study. Tumor depth limited to the subserosa (SS) was defined as serosal invasion negative (T-), while tumors with serosal invasion (SE, SI) were defined as serosal invasion positive (T+). The predictability of peritoneal recurrence based on sT and pT was evaluated using the Fine and Gray model. Cox regression analyses were performed for overall survival (OS) and relapse-free survival (RFS) with sT or pT as covariates., Findings: A total of 150 patients (37.9%) were sT+ and 82 (26.3%) were pT+. Sixty-two patients (15.7%) were sT+/pT+, 88 (22.2%) were sT+/pT-, 20 (5.1%) were sT-/pT+, and 226 (57.1%) were sT-/pT-. Both sT and pT were found to be independent predictors of peritoneal recurrence, OS, and RFS. The 5-year RFS rates of sT+/pT+, sT+/pT-, sT-/pT+, and sT-/pT-patients were 45.2%, 63.6%, 55.0%, and 81.8%, respectively., Conclusion: Intraoperatively diagnosed macroscopic serosal invasion showed a similar predictive value for peritoneal recurrence as pathologically diagnosed serosal invasion. The establishment of a novel staging system incorporating macroscopic serosal invasion is recommended., Competing Interests: Declaration of competing interest MT reports lecture fees from Taiho Pharmaceutical, Chugai Pharmaceutical, Ono Pharmaceutical, Bristol-Myers Squibb, Yakult Honsha, Takeda Pharmaceutical, Eli Lilly Japan KK, Pfizer Pharmaceutical, Daiichi Sankyo, Johnson and Johnson, Medtronic Japan, Intuitive Japan, Olympus outside the submitted work. JM reports the funding from National Cancer Center, Japan and the Ministry of Labour and Welfare, Japan for the present study, and personal fees from Chugai Pharmaceutical, outside the submitted work. TS reports personal fees from Taiho Pharma, Chugai Pharma, Ono Pharma, Eli Lilly, outside the submitted work. TY reports grants from Eli Lilly japan, personal fees from MSD, BMS, Ono, Taiho, Lilly, Chugai, Pfizer, Nihon Kayaku, Terumo, Otsuka, Myarisan, EA pharma, Astra-Zeneca, Covidien, Johnson and Johnson outside the submitted work. NB received a research grant from Ono and Takeda and honorarium from Taiho, Ono, Bristol-Myers Squibb outside the submitted work. MS reports lecture fees from Taiho Pharmaceutical and Eli Lilly, travel support from Eli Lilly outside the submitted work, and has served as Chairman of the board of directors of the Japan Gastric Cancer Association and member of the Guideline committee of the Japan Gastric cancer Association during the study period. All the other authors declare no competing interests. Red lines represent serosal invasion positive and blue lines represent serosal invasion negative. The C-index was calculated using the Fine and Gray model., (Copyright © 2022 Elsevier Ltd, BASO ~ The Association for Cancer Surgery, and the European Society of Surgical Oncology. All rights reserved.)