PURPOSE Optimal patient selection for neoadjuvant chemotherapy prior to surgical extirpation is limited by the inaccuracy of contemporary clinical staging methods in high-risk upper tract urothelial carcinoma (UTUC). We investigated whether the detection of plasma circulating tumor DNA (ctDNA) can predict muscle-invasive and non-organ confined (MI/NOC) UTUC. PATIENTS AND METHODS Plasma cell-free DNA was prospectively collected from chemotherapy-naive, high-risk UTUC patients undergoing surgical extirpation and sequenced using a 152-gene panel and low-pass whole-genome sequencing. To test for concordance, whole exome sequencing was performed on matching tumor samples. The performance of ctDNA for predicting MI/NOC UTUC was summarized using area under a receiver-operating curve and the optimal variant count threshold determined using Younden's J statistic. Kaplan-Meier methods estimated survival, and Mantel-Cox log-rank testing assessed the association between preoperative ctDNA positivity and clinical outcomes. RESULTS Of 30 patients prospectively enrolled, 14 were found to have MI/NOC UTUC. At least one ctDNA variant was detected from 21/30 (70%) patients with 52% concordance with matching tumor samples. Detection of at least two panel-based molecular alterations provided the optimal sensitivity and specificity to predict MI/NOC UTUC. Imposing this threshold in combination with a plasma copy number burden score >6.5 achieved a sensitivity of 79% and specificity of 94% in predicting MI/NOC UTUC. Furthermore, the presence of ctDNA was strongly prognostic for progression-free survival (1-yr PFS 69% vs. 100%, p<0.01) and overall survival (1-yr OS 56% vs. 100%, p<0.02). CONCLUSION The detection of plasma ctDNA prior to extirpative surgery was highly predictive of MI/NOC UTUC and strongly prognostic of PFS and OS. Preoperative ctDNA demonstrates promise as a biomarker for selecting patients to undergo neoadjuvant chemotherapy prior to nephroureterectomy.

DISCLOSURES BG Employment: Predicine Inc Stock: Predicine, Freenome, Myriad SJ Employment: Predicine, Inc, Roche/Genentech Stock: Predicine, Inc, Roche/Genentech WJS Advisory Board: Pacific Edge, Urogen GDG Stock: Natera Consulting: MyCareGorithm AN Employment: Bayer (immediate family member) Consultant/Advisory Role: Merck Sharp & Dohme, Roche, Bayer, AstraZeneca, Clovis Oncology, Janssen, Incyte, Seattle Genetics, Astellas, Bristol-Myers Squibb, Rainier Therapeutics, GlaxoSmithKline, Basilea Pharmaceuticals, Catalym Travel, Accommodation, Expenses: Roche, Merck Sharp & Dohme, AstraZeneca, Janssen, Rainier Therapeutics, Pfizer Other: Bayer (immediate family member) Stock or other ownership interest: Bayer (immediate family member) Honoraria: Roche, Merck, AstraZeneca, Janssen, Foundation Medicine, Bristol Myers Squibb, Astellas Pharm Research funding: Merck Sharp & Dohme (institution), AstraZeneca (institution), Ipsen, Gilead Sciences BMF Consulting: QED therapeutics, Boston Gene, Astrin Biosciences Advisory board: Merck, Immunomedics/Gilead, QED therapeutics, Guardant, Janssen Patent royalties: Immunomedics/Gilead Honoraria: Urotoday Research support: Eli Lilly Grants and research support: NIH, DoD CDMRP, Starr Cancer Consortium, P 1000 Consortium PD Employment: Predicine Inc Stock: Predicine, Inc RL Research support: Predicine; Veracyte; CG Oncology; Valar labs. Clinical trial protocol committee-CG Oncology. Scientific advisor/consultant-BMS, Merck, Fergene, Arquer Diagnostics, Urogen Pharma, Lucence.

This research was supported by the H Lee Moffitt Cancer Center & Research Institute; Predicine, Inc; and the American Cancer Society-Institutional Research Grant from January 1-December 31, 2021. EAS and ACS were the recipients of support from the Junior Scientist Research Partnership award from Moffitt Cancer Center and Research Institute.

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