Effect of treatment of residual disease after immunotherapy-based combinations on complete response rate in metastatic renal cell carcinoma.

601 Background: Immunotherapy (IO) has revolutionized the management of metastatic renal cell carcinoma (mRCC) by improving survival, overall response and complete response (CR) rates. CR is achieved in 11 to 17% with the different PD-1-based IO combinations in first-line setting of mRCC. However, local treatment of residual disease after systemic treatment exposure may improve CR rates. We performed a retrospective study to characterize patients (pts) in CR with systemic therapy alone or combined to an ablative approach of residual disease. Methods: We included all consecutive mRCC pts treated with mRCC in first-line treatment with IO combination with IO or TKI, either alone or with local treatment at the Institut de Cancérologie Strasbourg Europe. Pts were characterized according to IMDC risk group. Radiologic response was defined according to RECIST v1.1. Results: We enrolled 80 pts with mRCC between 5/2015 and 5/2022; median age was 68 (41-89) years; 75% male; 36 pts (45%) had prior nephrectomy; IMDC risk group: 12 favorable (15%), 50 intermediate (63%), 18 poor risk pts (22%), respectively; 47 pts (59%) received IO + IO, 24 (30%) received IO + TKI and 9 pts (11%) received another IO-based therapy; 35 pts (44%) achieved partial response, 23 pts (29%) stable disease, 13 pts progressive disease and 9 pts achieved CR (11%) as best response with systemic therapy alone; 10 pts out of 35 PR pts achieved CR by adding local treatment on residual disease. Among CR pts: 5 out of 19 pts had a component of sarcomatoid histology; median age was 60 years. Characteristics of pts with CR are reported in the table. Median duration of IO exposure before local therapy was 13 months. Residual disease resected sites included kidney (N = 6), lymph node (N = 4), lung metastasis (N = 2) and liver metastasis (N = 1). Local treatment was surgery for 9 pts and liver thermoablation for 1 patient. Conclusions: The resection of residual disease after first line IO-based therapy in mRCC improves CR rates (from 11% up to 24%). This approach should be considered as an option for a selected population. Prospective trials assessing this strategy should be performed in the future. Characteristics of patients in CR. [Table: see text]