Efficacy of immune checkpoint inhibitors in renal cell carcinoma venous tumour thrombus shrinkage (UroCCR 128).

Purpose: Surgery remains the cornerstone of localized renal cell carcinoma (RCC) care. Pembrolizumab has recently been recommended as a standard of care for RCC patients who are at high risk of recurrence. Data regarding the efficacy of ICIs either alone or in combination with ICIs or VEGF TKIs for VTT shrinkage are scarce.

Methods: In the framework of the French kidney cancer research network UroCCR (NCT03293563), we performed a retrospective multicentric European study to evaluate VTT shrinkage in patients treated with ICIs with metastatic or locally advanced renal cell carcinoma (RCC). The primary endpoint was the objective response rate (ORR) of patients with VTT to ICI-based therapy. Radiological assessment was performed by a treating physician according to the RECISTv1.1 criteria.

Results: We included 44 patients. The median age was 69 years (range 37-88). All patients was intermediate or poor IMDC risk group. Twenty-three patients were treated with anti-PD-1 in combination with anti-CTLA-4 therapy, 13 patients with ICI monotherapy, and 8 patients with ICIs in combination with antiangiogenic TKI. At baseline, the median VTT diameter was 22 mm (range 7-93). After a median duration of treatment of 5.8 months (range 1.8-39.1), the ORR was 38% (n = 17), including 4 complete responses (CRs) and 13 partial responses (PRs). Ten patients had stable disease (SD), and 17 had progressive disease (PD) as the best response of the VTT.

Conclusion: These data highlight the potential efficacy of ICIs to shrink the VTT even if they seem to have little impact on the extent of VTT.