Real world analysis of peritoneal metastasis from renal cell carcinoma: Meet-Uro 27 study.

638 Background: Peritoneal metastases (PM) have been reported in approximately 1% of patients (pts) 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 RCC pts with PM treated as per clinical practice. Methods: Baseline characteristics and outcome data of pts with PM from RCC were retrospectively collected from 12 Italian oncological referral centers adhering to the Meet-Uro group, from January 2016 to September 2022. Results: We collect 91 RCC pts with PM. 87/91 pts received systemic treatment, 4/87 only best supportive care. First line treatment included TKI and ImmuneOncology(IO)-TKI with different Objective Response Rate(ORR) (41% vs 53.8%, respectively) and Disease Control Rate (DCR) (57.1% and 80.7%, respectively) as well as median PFS (9.9 mo (95%CI 4.5-15.4) for TKI and not reached (NR) for IO-TKI (69.7% pts were free from progression at a median follow up of 13.8 months). Primary refractory (PR) pts were 35.7% for TKI and 7.7% for IO-TKI. According to IMDC score, mPFS was consistent among risk categories, 36.8 mo (95%CI 9.6-63.9) for good risk pts, 13.8 mo (95%CI 8.8-18.8) for intermediate pts and 2.9 mo (95%CI 2.2-3.7) for poor risk pts. Synchronous PM was associated to shorter mPFS 11.0 (95%CI 3.1-19.0) compared to patients with metacronous involvement as well as ORR (31.3%) and DCR (43.1%) whereas PR was higher (34.7%). Only 43/87 pts (45.7%) received a second line treatment that was TKI ( ORR 30.7%; DCR 61.5%; or IO (ORR 20.6%; DCR 41.3%). mOS was 21.8 mo (12.0-31.5) for TKI and NR for pts treated with IO-TKI (80.8 alive at 1 yrs). According to IMDC score, mOS was NR for good risk pts, 24.6 (95%CI 15.8-33.3) and 3.4 (95%CI 2.4-4.3) for intermediate and poor risk, respectively. Conclusions: We report one of the largest case series regarding PM from RCC. Poor risk patients according to IMDC score, sarcomatoid feature and liver metastasis were more represented in our population, compared to historical control, suggesting a more aggressive behavior of PM mRCC. Outcome data suggest that TKI-IO as first line treatment, compared to TKI monotherapy, and TKI as second line, compared to IO, are more active treatment for these pts with dismal prognosis. Nevertheless, synchronous PM has been reported in 57% of pts with poorer outcome and lower response rate. [Table: see text]