Abstract CT106: Primary tumor response in T1aN0M0 renal cell carcinoma patients ineligible for surgery and treated with nivolumab and ipilimumab: Results from phase 2 pilot study
Authors: Tsimafeyeu Ilya , Volkova Maria , Gafanov Rustem , Myslevtsev Igor , Andrianov Andrey , Bex Axel 
Published: June 2022

Background: Some patients with primary renal cell carcinoma (RCC) are unable to have surgery for different reasons (functional single kidney with a central, high-complexity RCC, high risk of nephrectomy and dialysis, patients with complex coagulation disorders, etc.). We hypothesize that combination of nivolumab and ipilimumab could eliminate the primary tumor in T1aN0M0 patients ineligible for surgical treatment.

Methods: This is a prospective, multicenter, non-randomized phase 2 pilot study. Patients with biopsy-proven clear-cell RCC of ≤4 cm (cT1a), no evidence of any metastases, and unable to have surgery or other nephron-sparing interventions (ablation) or with preference to have no surgery or intervention for any reason received combination of ipilimumab (1 mg/kg intravenously) every 3 weeks for four doses, and nivolumab (240 mg intravenously) every 2 weeks during 16 weeks. The primary endpoint was complete response rate. Simon's two-stage design was used. The null hypothesis that the true complete response rate was 11% and was tested against a one-sided alternative. This design yields a type I error rate of 0.05 and power of 0.9 when the true complete response rate is 60% (alternative hypothesis). The null hypothesis should be rejected if 3 or more responses are observed in 8 patients.

Results: Between February 2020 and June 2021, 8 patients were included. Median age was 77.9 years (range 73-89). Patients were Caucasian (100%), predominantly male (75%), 62.5% had centrally located RCC, 25% had ECOG PS 1, and 6 of 8 patients had moderate and severe comorbidities. Median follow-up was 12.7 months (95% CI 5.2-16.5). All patients received immunotherapy during 4 months without grade ≥2 adverse events. No complete responses were observed. Partial responses were found in 2 patients (25%). Median size of the primary tumor at RCC diagnosis and after immunotherapy was 3.11 cm (range 2.2-3.9) and 2.86 cm (range 1.5-4.0), respectively. Any shrinkage of the primary tumor was reported in 4 (50%) patients (change in median sum of diameters -18%). Only one patient had tumor enlargement (+0.5 cm (+13%) after 9 months. SBRT was used in this patient. All other patients are under active surveillance. Next secondary end-point of 3-year progression-free survival will be reported.

Conclusions: The activity of immunotherapy against primary tumor was limited in patients with T1aN0M0 RCC ineligible for surgical treatment. Duration of stable disease will be studied with long-term follow-up of these patients. Treatment with nivolumab and ipilimumab was safe in patients with moderate and severe comorbidities.

Citation Format: Ilya Tsimafeyeu, Maria Volkova, Rustem Gafanov, Igor Myslevtsev, Andrey Andrianov, Axel Bex. Primary tumor response in T1aN0M0 renal cell carcinoma patients ineligible for surgery and treated with nivolumab and ipilimumab: Results from phase 2 pilot study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT106.