32: Initial Findings from the Multi-Institutional Sarcomatoid Renal Cell Carcinoma Consortium (SaRCC)

Background: Sarcomatoid renal cell carcinoma (sRCC) is a rare histological subtype of RCC that carries a poor prognosis. Understanding sRCC tumor biology and optimization of treatment has been limited by its rarity and subsequent paucity of data. Here we present the initial descriptive analysis of sRCC data spanning multiple decades from a multi-institutional consortium dedicated to determining the underpinnings of sRCC.

Methods: A multi-institutional retrospective analysis of patients with sRCC that underwent nephrectomy was conducted. We identified 1022 patients from 4 sites (Memorial Sloan Kettering: n=228, UCLA: n=226, MD Anderson: n=423, Mayo Clinic: n=145) between 1986-2019. Survival was calculated based on death or last known follow-up. Demographic data, clinical presentation, and survival outcomes were captured and analyzed.

Results: The cohort consisted of 708 (69.3%) males and 314 (30.7%) females. Post-surgical median follow-up was 14.6 months (IQR 5.7-40.2). 563 (80.2%) presented with systemic symptoms such as fatigue/hematuria, and 139 (19.8%) were incidentally discovered. Preoperatively, 656 (64.2%) were metastatic, while 366 (35.8%) were localized on imaging. 83 (12.6%) patients underwent neoadjuvant chemotherapy. Final specimen AJCC stage distribution was 9.3% (92) Stage I, 8.6% (85) Stage II, 66.5% (655) Stage III, and 15.5% (153) Stage IV. Most common histology was clear-cell 78.0% (764), followed by 5.0% (49) chromophobe, 4.2% (41) papillaryNOS, 2.3% (23) papillary-type2, and 2.0% collecting-duct (20) with 5.6% (55) unclassified. In those with clinically localized disease, recurrence occurred in 57.5% (369); 83.8% (218) had distant recurrence, with 11.2% (29) local, and 5.0% (13) regional. At last follow-up 16.0% (157) were NED, 14.6% (144) AWD, 63.7% (626) DOD, and 5.7% (56) dead of unknown causes. Median CSS was 10.9 months, and median OS was 11.2 months.

Conclusions: sRCC typically presents as advance disease (stage III or greater) with symptoms commonly present. Most localized patients without evidence of distant metastasis will recur despite tumors treated with nephrectomy.