HER2 status	Grade I recommendations	Grade II recommendations	Grade III recommendations
Positivei	Trastuzumab combined with oxaliplatin/cisplatin + 5‐FU/capecitabine (Evidence 1A)	Trastuzumab combined with oxaliplatin/cisplatin + tegafur (Evidence 2B)	Trastuzumab combined with other first‐line chemotherapy regimens, excluding anthracyclines (Evidence 3)
Negativeb‐f	Oxaliplatin + fluorouracil (5‐FU/capecitabine/tegafur) (Evidence 1A)	Three‐drug combination regimens, i.e. DCF and mDCF (Evidence 1B) for patients in good physical conditions and with large tumor burden
	Paclitaxel/docetaxel + fluorouracil (5‐FU/capecitabine/tegafur) (Evidence 2A)
	Cisplatin + fluorouracil (5‐FU/capecitabine/tegafur) (Evidence 1A)
	For PD‐L1 CPS≥5 patients, Chemotherapy (FOLFOX/XELOX) combined with nivolumab (Evidence 1a) m,n.		For PD‐L1 CPS≥1 patients, pembrolizumab monotherapy can be recommendedn

Abbreviations: HER2, human epidermal growth factor receptor 2; 5‐FU, 5‐fluorouracil; ECF, Epirubicin + Cisplatin + 5‐FU; DCF, Docetaxel + Cisplatin + 5‐FU; mDCF, modified DCF; FOLFOX, leucovorin calcium + 5‐FU + oxaliplatin; XELOX, capecitabine + oxaliplatin; PD‐L1 CPS, programmed death ligand‐1 combined positive score;