Perioperative or neoadjuvant chemotherapy for locally advanced gastric or gastroesophageal junction cancer: from independent evidence in the West, the East, and Japan to global collaboration.

The survival outcome of patients with locally advanced gastric or gastroesophageal junction (G/GEJ) cancer remains unsatisfactory, and improvements in survival and recurrence remain urgent issues for clinicians worldwide. Prior to the 2000s, locally advanced G/GEJ was a different disease between the West and the East regarding diagnosis, surgery, and prognosis. However, recent advances in medical oncology have set the stage for harmonization. Herein, this review highlights clinical trials of perioperative or neoadjuvant chemotherapy conducted during the past two decades to provide insights into future directions. We focused on pivotal clinical trials of perioperative or neoadjuvant chemotherapy for patients with locally advanced G/GEJ cancer. We paid special attention to the indication and oncological outcomes of perioperative or neoadjuvant chemotherapy. The attempts to investigate the optimal treatment strategy for locally advanced G/GEJ cancer over the past 20 years have resulted in a global consensus on the necessity of perioperative or neoadjuvant chemotherapy, although there have been different circumstances regarding treatment for G/GEJ cancer among the West, the East other than Japan, and Japan. Two randomized global phase III trials, the KEYNOTE-585 and MATTHERHORN, were successfully accomplished for a common indication. Furthermore, perioperative immunotherapy suggested a new indication with molecular biomarkers such as microsatellite status or PD-L1 status beyond the conventional tumor-lymph node-metastasis (TNM) staging system. Global studies provide the stage for discussing the future optimal indication of neoadjuvant chemotherapy, opening the door for future global collaborations to better treat patients with locally advanced G/GEJ cancer.