Molecular alterations across sites of metastasis in patients with renal cell carcinoma (RCC).
Authors: McKay Rana R. , Barata Pedro C. , Elliott Andrew , Bilen Mehmet Asim , Burgess Earle F , Darabi Sourat , Dawson Nancy Ann , Gartrell Benjamin Adam , Hammers Hans J. , Heath Elisabeth I. , Magee Daniel , Rao Arpit , Ryan Charles J. , Twardowski Przemyslaw , Wei Shuanzeng , Zhang Tian , Zibelman Matthew R. , Nabhan Chadi , Korn W. Michael , Gulati Shuchi 
Published: February 2022

287 Background: RCC has a distinct pattern of metastatic spread with common sites of metastasis including the lung, bone, and liver. Less common sites include the brain, adrenal gland, and pancreas. While the pattern of metastatic spread has prognostic significance, the biology driving tropism to specific organ sites has not been fully characterized. We utilized a multi-institutional real-world dataset to examine genomic alterations and transcriptional signatures across the spectrum of metastatic sites in patients with RCC. Methods: RCC tissue specimens derived from the kidney and distant metastatic sites were sequenced utilizing a commercially available Clinical Laboratory Improvement Amendments (CLIA)-certified assay by Caris Life Sciences. Whole exome and transcriptome sequencing was performed. Molecular subgroups were defined according to the IMmotion151 metastatic RCC subtypes, with subgroups determined by a weighted average of gene expression levels. Molecular analysis and PD-L1 expression (SP142) were described by metastasis site. Results: 657 RCC samples from 653 patients underwent molecular profiling. The median age was 62 years (range 14-90) and the majority were male (70.6%). The most common histology was clear cell RCC (n = 509, 77.5%), followed by papillary (n = 63, 9.6%), chromophobe (n = 30, 4.6%), medullary (n = 8, 1.2%), collecting duct (n = 6, 0.9%), and mixed (n = 41, 6.2%). Specimen source included the kidney (n = 340, 51.8%), lung (n = 75, 11.4%), bone (n = 45, 6.8%), lymph nodes (n = 34, 5.2%), liver (n = 28, 4.3%), endocrine glands (adrenal, pancreas, and thyroid; n = 23, 3.5%), brain/CNS (n = 16, 2.4%), and other metastatic sites (n = 96, 14.6%). Compared to kidney, several genes were mutated at higher rates for select metastatic sites, including PBRM1 (59.5% bone, 59.1% endocrine, and 45.9% lung vs 33.8% kidney, p< 0.05) and KDM5C (27.8% endocrine, 29.2% lymph nodes, and 35.3% soft tissue vs 9.3% kidney, p< 0.05). When evaluating metastatic specimens versus kidney specimens, bone metastases had a significantly higher proportion of tumors classified as ‘Angio/stromal’ (n = 19, 42.2%; vs n = 52, 15.4%; p< 0.0001), while liver metastases had a higher proportion of the ‘complement/Ω-oxidation’ subgroup (n = 17, 60.7%; vs n = 48, 14.1%; p< 0.0001). PD-L1 expression in metastatic sites (range 6.8%-21.7%, with exception of 0% in GI; p= 0.09 to 0.99) was not significantly different from the kidney (16.6%). Conclusions: In our contemporary real-world analysis, we demonstrate differential patterns of molecular alterations among sites of metastasis in RCC. Our observations elucidate the biology underlying heterogeneous disease outcomes associated with site of metastasis. Application of predictive signatures by site of metastasis may help inform personalized therapy strategies in advanced RCC. Further studies are warranted to validate our findings.