Background: Immune checkpoint inhibitors (ICI) have demonstrated impressive activity in metastatic clear-cell renal cell carcinoma (ccRCC) and have become standard treatment options for patients with advanced disease. Data supporting the effectiveness of ICI-based therapy in advanced non-clear cell RCC (nccRCC) is more limited.
Methods: We performed a retrospective analysis using the International Metastatic RCC Database Consortium (IMDC) to evaluate the outcomes of patients with advanced nccRCC. Patients were classified into three groups based on first-line therapy: ICI-based therapy (monotherapy or combination), vascular endothelial growth factor (VEGF) inhibitor monotherapy, or mammalian target of rapamycin (mTOR) inhibitor monotherapy. The primary outcome was overall survival (OS). Secondary outcomes were time to treatment failure (TTF) and objective response rate (ORR). We used the Kaplan-Meier method to compare OS and TTF between treatment groups and Cox proportional hazards models to adjust for prognostic covariates.
Results: We identified a total of 1145 patients with metastatic nccRCC. The most common subtype was papillary RCC (54.9%). For first-line therapy, 74.3% received VEGF monotherapy, 15% received mTOR monotherapy, and 10.7% received ICI-based therapy. Median OS in the ICI group was 28.6 months, versus 16.4 months in the VEGF group and 12.2 months in the mTOR group. Median TTF in the ICI group was 6.9 months, versus 5.0 months in the VEGF group and 3.9 months in the mTOR group. ORR was 27.2% in the ICI group, 14.5% in the VEGF group, and 9% in the mTOR group. After adjusting for the IMDC risk group, histological subtype, and age, the hazard ratio for OS was 0.57 (95% CI 0.42-0.78, p < 0.0001) for ICI versus VEGF and 0.50 (95% CI 0.36-0.71, p < 0.0001) for ICI versus mTOR.
Conclusions: In advanced nccRCC, first-line ICI-based treatment appears to be associated with improved OS compared to VEGF and mTOR targeted therapy. These results should be confirmed in prospective randomised trials.
Keywords: Immune checkpoint inhibitor; Immunotherapy; Kidney cancer; Non-clear cell RCC; Renal cell carcinoma; Variant histology RCC.
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