Comparative analysis of dual immune checkpoint inhibitor combination therapy versus immune checkpoint inhibitor plus tyrosine kinase inhibitor combination therapy for renal cell carcinoma with inferior vena cava tumor thrombosis.

Background: Whether immune checkpoint inhibitor (ICI) plus ICI combination therapy or ICI plus tyrosine kinase inhibitor (TKI) combination therapy is useful for renal cell carcinoma (RCC) with inferior vena cava tumor thrombosis (IVCTT) remains unclear.

Methods: We retrospectively evaluated the therapeutic effects and incidence of treatment-related adverse events (TRAEs) associated with ICI-based combination therapy in 36 patients with advanced RCC with IVCTT.

Results: The median age at initiation of treatment was 71 years; the IVCTT stages were cT3b in 22 patients and cT3c in 14. The ICI-ICI and ICI-TKI groups comprised 15 and 21 patients, respectively. Median tumor shrinkage at the best response showed that the primary tumor diameter decreased by 1.8 cm (22%), and the IVCTT height decreased by 1.5 cm (26%). A higher proportion of patients in the ICI-TKI group experienced tumor shrinkage than those in the ICI-ICI group (primary tumor, p = 0.0325; IVCTT, p = 0.0112). Approximately 27% of patients experienced an increase in the IVCTT height with ICI-ICI combination therapy. No significant difference was observed in the relative tumor shrinkage of IVCTT, primary or level-down staging of IVCTT, other treatment effects, incidence of TRAEs, surgical outcomes, or prognosis between the groups.

Conclusion: ICI-based combination therapy is effective against IVCTT and primary RCC. Although ICI-ICI is associated with a higher probability of tumor growth compared with ICI-TKI in the frequency of tumor regression, both therapies may be almost equally effective against primary RCC with IVCTT.