Primary resistance to nivolumab plus ipilimumab therapy affects second-line treatment outcomes in patients with metastatic renal cell carcinoma.

Nivolumab plus ipilimumab (NIVO+IPI) has a long-term response rate of 30% for patients with metastatic renal cell carcinoma (mRCC). However, 20% of patients develop primary resistant disease (PRD) to NIVO+IPI and show poor survival outcomes. In this study, we aimed to evaluate the effect of PRD as a second-line treatment in patients with mRCC. The data used in this multi-institutional, retrospective cohort were collected between August 2015 and January 2023. In total, 189 patients with mRCC were treated with NIVO+IPI and then with a vascular endothelial growth factor receptor-tyrosine kinase inhibitor. Associations between PRD and progression-free survival of second-line treatment (PFS), progression-free survival 2 (PFS2), and overall survival (OS) were analyzed. The median age at NIVO+IPI initiation was 67 years in the male-dominant population (n = 140, 74.1%), and most patients had clear cell histology (n = 140, 74.1%). PRD was recorded in 42 (22.2%) of 189 patients during NIVO+IPI therapy. Patients who experienced PRD showed poor PFS (hazard ratio [HR], 1.788; 95% confidence interval [CI], 1.176-2.718; p = 0.007), PFS2 (HR, 4.127; 95% CI, 2.649-6.431; p < 0.001), and OS (HR, 3.330; 95% CI, 2.040-5.437; p < 0.001). Before starting second-line therapy, patients with PRD tended to have a poor performance status compared with non-PRD patients and a higher IMDC risk. Second-line drug therapy was not associated with treatment outcomes in patients with PRD. PRD in patients with mRCC receiving NIVO+IPI as first-line treatment was associated with poor clinical course, even with second-line therapy.