Abstracts from the Abstracts from the Mid-Atlantic Section of the AUA 2021

© The Canadian Journal of Urology TM : International Supplement, October 2021 Moderated Poster Session 4: Kidney/Bladder/Penile/Testicular/ Adrenal Cancer Characterizing Tumor Thrombus Arising from Non Clear Cell Renal Cell Carcinoma M. Rabinowitz 1 , T. Esfandiary 1 , J. Cheaib 1 , S. Patel 1 , R. Alam 1 , M. Metcalf 1 , D. Enikeev 2 , M. Allaf 1 , Y. Ged 1 , P. Pierorazio 1 , N. Singla 1 1 The Johns Hopkins University School of Medicine, Baltimore, MD, USA; 2 Sechenov University, Moscow, Russian Federation Introduction andObjective: Renal cell carcinoma (RCC) can exhibit a unique vascular tropism that enables local tumor thrombus extension into the renal vein and inferior vena cava (IVC). While most tumor thrombi forming RCCs are of clear cell (cc) histology, non-clear cell (ncc) subtypes can also exhibit this pattern. We sought to characterize clinicopathology and survival outcomes among patients with IVC tumor thrombus arising fromccRCCversus nccRCC. Methods: A retrospective single institutional analysis was performed on all patients diagnosed with IVC tumor thrombus secondary to RCC (pT3b-c) from 1996-2021. Clinicopathology was compared by histology. Recurrence- free survival (RFS), overall survival (OS), and cancer-specific survival (CSS) were assessed using Kaplan-Meier methods and Cox regression. Results: We identified 103 patients with IVC thrombus in the setting of RCC, including 82 ccRCC and 21 nccRCC (20.4%). There were no statistically significant differences in age, sex, bodymass index, or smoking status between the ccRCC and nccRCC patients. Among patients with nccRCC, papillary was the most common histology (52.4%). Patients with nccRCC were more likely to have regional lymph node involvement (42.9% vs. 20.7%, p=0.04). No differences in surgical margin status, perioperative outcomes, or need for IVC resection or reconstruction were observed between cohorts. Median RFS for nccRCC vs. ccRCC was 30 vs. 53 months, respectively (p = 0.1). Median OS was 32 (nccRCC) vs. 39 (ccRCC) months (p=0.7), while median CSS was 44 (nccRCC) vs. 49 (ccRCC) months (p=0.5) (Figure 1). Conclusions: Patients with nccRCC can develop IVC tumor thrombus. Those with IVC tumor thrombus extension from nccRCC or ccRCC exhibit similar perioperative and oncologic outcomes. Our results suggest that the surgical management for RCC patients with tumor thrombus need not differ by histology. MP4-13 PercutaneousMicrowave Ablation vs. Partial Nephrectomy for Small Renal Masses: Cost-Effectiveness Analysis C. Yeaman, J. Lobo, A. DeNovio, L. O’Connor, R. Marchant, C. Ballantyne, N. Schenkman University of Virginia, charlottesville, VA, USA Introduction andObjective: To perform a cost-effectiveness analysis using a Markovmodel between percutaneous microwave ablation (MWA) and partial nephrectomy (PN) for treatment of small renal masses using both literature values and institutional outcome data. Methods: We created a decision analytic Markov model depicting management of the small renal mass (percutaneous MWAvs robotic-assisted PN (RA-PN) incorporating costs, health utilities, and probabilities of complications and recurrence as model inputs from the literature. Modeling was performed using Treeage (2020.2.1). Awillingness to pay (WTP) threshold of $75,000 was used. Results: MWA was the preferred treatment modality. MWA dominated RA-PN, meaning it resulted in more QALYs at a lower cost. Model inputs are shown in Table 1 and the model decision tree is shown in Figure 1. Cost- effectiveness analysis revealed an Incremental Cost Effectiveness Ratio (ICER) of -$6,847 per QALY. Themodel revealedMWAhad amean cost of $12,921 and 12.5 QALYs. RA-PN had a mean cost of $21,477 and 11.2 QALYs. Sensitivity analysis was performed for all variables. Patient age of 39 years or younger resulted in RA-PN being favored over MWA. Relative preference of MWA was robust to sensitivity analysis of all other variables. Cost of RA-PN and patient age had the most dramatic impact on ICER. RA-PN was more cost- effective if local recurrence was managed with MWA rather than partial or radical nephrectomy. Conclusions: MWA is preferred cost-effective for treatment of small renal masses when compared with RA-PN and accounting for complication and recurrence risk. MP4-12 30