Higher MCR-SM was significantly associated with older age (≥71), recurrence GC rather than unresectable GC, higher BMI at ICIs therapy (≥19.72%), higher MCR-BW (≥ −0.231%), IrAEs occurrence, higher serum albumin (≥3.4), and higher prognostic nutrition index (≥ 39.815) (P = 0.006, 0.03, 0.008, 0.01, 0.01, 0.004, 0.008, respectively). The gene discussed is ALB; the disease is gastric cancer.