Observational study of tislelizumab (Tisle) combined with pazopanib in reducing venous tumor thrombus in clear cell renal cell carcinoma with venous invasion.

481 Background: Renal cell carcinoma with venous tumor thrombus (RCC-VTT) presents significant surgical challenges, often requiring complex interventions. Neoadjuvant therapies that can reduce primary tumor size and venous tumor thrombus may simplify surgical procedures and decrease associated risks. Methods: The data of pts with RCC-VTT who underwent Tisle combined with Pazopanib neoadjuvant therapy at the First Affiliated Hospital of Xinjiang Medical University from Nov. 2021 to Jan. 2024 were analyzed. Inclusion criteria were as follows: (1) age ≥ 18 years; (2) TNM stage T3-4N0-1M0-1; (3) Eastern Cooperative Oncology Group (ECOG) performance status ≤ 1; (4) a life expectancy of at least 3 months; and (5) adequate bone marrow, kidney, liver function, and normal blood test results. Exclusion criteria were as follows: (1) prior treatment with other antitumor drugs; (2) recent history of cardiac or vascular events or other conditions precluding surgical treatment; (3) participation in other clinical trials within the past 3 months; (4) lack of legal capacity or limited legal capacity; and (5) contraindications, allergies, or adverse reactions to pazopanib and tislelizumab. Eligible Pts received Tisle 200 mg IV. in day 1(D1), every 21 days for 4 cycles; Pazopanib was administered orally at a dose of 800 mg once daily for 12 weeks prior to the scheduled surgery. The primary endpoint of the study was the percentage change in the length of the VTT and the percentage reduction in the longest tumor diameter. Results: Nine patients with a median age of 58 years were treated. The median reduction in tumor diameter was 31.0% (range: 3.0%–48.7%), and the median reduction in VTT length was 29.2% (range: -153.1% to 100.0%). Treatment led to decreased surgical complexity in 88.9% of patients. The regimen was well-tolerated, with manageable adverse events primarily including vomiting, itching, and weight loss. No metastasis developed during the study period, though one patient required expedited surgery due to an increase in thrombus size. Conclusions: The combination of tislelizumab and pazopanib as neoadjuvant therapy effectively reduces the size of tumors and associated venous tumor thrombi in patients with RCC-VTT, facilitating less complex surgical interventions and potentially leading to better postoperative outcomes.