CA19-9 in combination with P-CRP as a predictive marker of immune-related adverse events in patients with recurrent or unresectable advanced gastric cancer treated with nivolumab

BACKGROUND: Immune-check point inhibitors (ICPIs) for treatment of cancer patients sometimes induce potentially life-threatening immune-related adverse events (irAEs), which predict ICPIs treatment efficacy. Prediction of irAEs would be useful for management of irAEs and prediction of ICPIs efficacy. This study aimed to determine predictors of irAEs in patients with recurrent or unresectable advanced gastric cancer (RUGC) treated with nivolumab. METHODS: Seventy-eight RUGC patients treated with nivolumab at nine institutions between January 2017 and April 2020 were included in this study. The usefulness of specific blood test results as predictors of irAEs was evaluated. RESULTS: We observed irAEs in 15 (19.2%) patients. The disease control rate was significantly higher in the patients with irAEs than in those without (86.7% vs. 42.9%; P < 0.001). The median progression-free survival was significantly longer for patients with irAEs than for patients without (4.9 vs. 2.6 months; P = 0.018). The median survival time was longer for patients with irAEs than for those without (9.4 vs. 5.8 months; P = 0.041). The receiver operating characteristic (ROC) curves for irAEs indicated that the area under the curve (AUC) of carbohydrate antigen 19–9 (CA19-9) was highest (0.692; P = 0.022), followed by that for the platelet count × serum C-reactive protein (P-CRP) value (0.680; P = 0.032). The AUC for the CA19-9 + P-CRP combination was 0.782, which was more useful than that for either component and significantly associated with overall survival of nivolumab-treated RUGC patients. CONCLUSIONS: The CA19-9 + P-CRP combination was predictive of irAEs and prognosis in RUGC patients.