Risk of Thromboembolism in Patients Receiving Immunotherapy-Based Combinations as Front-Line Therapy for Metastatic Renal Cell Carcinoma

Background: Most patients with treatment-naïve metastatic renal cell carcinoma (mRCC) receive combination-based immunotherapy with either 2 immune-oncology checkpoint inhibitors (IO/IO) or an IO agent in combination with a vascular endothelial growth factor receptor (VEGF-R) tyrosine kinase inhibitor (IO/TKI). The rates of thromboembolism (TE) in these cohorts are not clearly described and can potentially impact decision-making between IO/IO and IO/TKI.

Methods: We conducted a retrospective investigation of patients with treatment-naïve mRCC treated with IO-based combinations between January 2015 and April 2021 at the Cleveland Clinic. TE events, including venous and arterial, were identified in each group. Competing risk regression was done to identify factors associated with the development of TE following therapy, with all-cause mortality treated as a competing event.

Results: Of 180 patients identified, 77 (43%) received IO/TKI and 103 (57%) received IO/IO. Median age was 65 years, 75% were male, and 80% had clear cell histology. Baseline characteristics were similar between the 2 groups. At a median follow-up of 22.0 months, 10.0% of all patients had a TE. The one-year incidence of TE was 8.1% (95% CI: 3.3%-15.8%) with IO/TKI and 9.8% (95% CI: 5.0%-16.5%) with IO/IO and was not significantly different between the 2 groups (HR 0.89, 95% CI: 0.35%-2.28%). Occurrence of TE was associated with decreased overall survival regardless of IO/IO or IO/TKI therapy (HR 2.80, 95% CI: 1.57-5.02). There was no difference in incidence of TE based on patient age, gender, prior history of TE, International Metastatic Renal Cell Carcinoma (IMDC) risk group, or Khorana score.

Conclusions: Incidence of TE is similar between IO/IO and IO/TKI regimens in treatment-naïve mRCC and is also associated with decreased overall survival. While risk of TE may not guide decision-making in choice of front-line mRCC therapy, careful attention should be given to the high risk of TE in this population.