Real world analysis of peritoneal metastasis from renal cell carcinoma. Meet-Uro27.

Background Peritoneal metastases (PM) have been reported in approximately 1% of patients with metastatic Renal Cell Carcinoma (mRCC). Outcome data are limited due to the rarity of this metastatic site. Therefore, the aim of our study is to describe renal cell carcinoma (RCC) patients with PM treated as per clinical practice. Methods Baseline characteristics and outcome data of patients with PM from RCC were retrospectively collected from 18 Italian oncological referral centers adhering to the Meet-Uro group, from January 2016 to January 2023. Results We collect 81 RCC patients with PM. 78/81 received systemic treatment, 3/81 only best supportive care. First line treatment included tyrosine-kinase inhibitors (TKI) (46/78), ImmuneOncology (IO)-TKI (26/78) and IO-IO (6/78), with different Objective Response Rate (ORR) (43.4% in TKI monotherapy group vs 50% in IO-TKI group, respectively) and Disease Control Rate (DCR) (60.8% in TKI treated patients vs 76.9% in IO-TKI treated patients). Median PFS was 6.4 months (95%CI 4.18-14.8) in patients treated with TKI monotherapy vs 23.7 months (95%CI 11.1-NR) in patients treated with IO-TKI (p 0.015). The median OS (mOS) was 22.7 months (95%CI 13.32 – 64.7) in the TKI monotherapy group vs 34.5 mo (95%CI NR-NR) in the IO-TKI group with 53.8% of patients alive at 1 years in the latter group, (p 0.16). Primary refractory patients were 36.9% for TKI and 15.3% for IO-TKI. According to International Metastatic renal cell carcinoma Database Consortium (IMDC) score, mPFS and mOS were consistent among risk categories. Median PFS was 36.6 months (95%CI 10.9-NR) for good risk patients compared to 10 months (95%CI 7.5-29.8) for intermediate risk and 2.96 months (95%CI 2.43-11.28) for poor risk population (p <0.0005) whereas mOS was NR (95%CI 28.65-NR) for good risk patients compared to 35.3 months (95%CI 24.6-NA) and 12.4 months (95%CI 3.52-NR) for intermediate and poor risk population, respectively, (p 0.0002). Only 34/78 (43.5%) received a second line treatment that was TKI (ORR 8.3% and DCR 41.6%) or IO (ORR 18.1% and DCR 40.9%). Conclusion We report one of the largest case series regarding PM from RCC. Characteristics of patients suggest a more aggressive behavior of PM from mRCC. Outcome data suggest that TKI-IO as first line treatment, and TKI as second line, confirm their activity for these patients with dismal prognosis.