Abstract 2178: Circulating tumor DNA (ctDNA) correlates closely with tumor necrosis and relapse-free survival (RFS) in hepatocellular carcinoma (HCC) patients treated with perioperative cemiplimab

Purpose: We evaluated ctDNA as a pharmacodynamic and predictive biomarker in patients (pts) with resectable HCC treated with cemiplimab (anti-programmed cell death-1). Background: A biomarker-focused study of neoadjuvant cemiplimab in resectable HCC demonstrated acceptable safety and pathologic responses that were associated with immune signatures of intratumoral T-cell response (Marron TU et al. Lancet Gastroenterol. Hepatol. 2022). ctDNA is emerging as a tool to monitor therapy responses and predict RFS in perioperative HCC studies. Methods: We enrolled 21 pts who received 2 cycles of neoadjuvant cemiplimab (350 mg intravenous every 3 weeks), followed by surgical resection and 8 cycles of adjuvant cemiplimab (NCT03916627). The primary endpoint was significant tumor necrosis (STN; >70% necrosis). Secondary endpoints included safety, RFS, and overall survival. A post hoc analysis examined pathological response (≥50% necrosis). Pts underwent pretreatment biopsies and longitudinal blood collection for ctDNA analyses using bespoke multiplex PCR-next generation sequencing (Signatera). We evaluated correlatives of ctDNA changes and the prognostic value undetectable ctDNA after surgery on RFS. Results: Median pt age was 68 years; 52% were Asian, 43% white, and 5% Black; 19% were also Hispanic; 62% had a history of viral hepatitis. ctDNA measurements at baseline and after 1 dose of cemiplimab were available from 19 pts who completed neoadjuvant cemiplimab and underwent successful surgical resection. Pre-surgical absolute ctDNA levels decreased by >50% in 10 pts, including all with greater than 50% tumor necrosis. As of August 1, 2022; median follow-up for the adjuvant period was 23 months (interquartile range: 20-26 months). 8 pts of the 19 pts have relapsed. Pts with a >50% decrease in ctDNA had median RFS of 28 months (95% CI 10, 28), vs 17 months (95% CI 4, not evaluable [NE]) in those with ≤50% decrease in ctDNA. 17 pts had a baseline ctDNA measurement, surgical resection, and data following surgery. ctDNA detection following surgery was associated with disease relapse (Fischer’s exact test, p=0.015), shorter RFS (median 10 months, 95% CI: 4, 28) compared to ctDNA-negative pts (not reached, 95% CI 13 months, NE; hazard ratio 0.14, p=0.006), and identified molecular relapse based on ctDNA with a median lead time of 5 months before imaging relapse. 20 pts (95%) were alive at last follow-up. Interpretation: Changes in ctDNA identify early response to immunotherapy more accurately than standard modalities such as imaging, correlating closely with pathological responses and RFS. ctDNA monitoring during neoadjuvant treatment and following surgery may identify pts with early antitumor responses, improve the prediction of disease relapse or RFS, and inform additional early treatment decisions. Citation Format: Thomas U. Marron, Laura Brennan, Pauline Hamon, Maria Isabel Fiel, Stephen C. Ward, Yuan O. Zhu, Edward Kim, Alice O. Kamphorst, Pradeep Thanigaimani, Thomas S. Uldrick, Natalie Lucas, Kathy Wu, Olivia Hapanowicz, Paula King, Siyu Li, Elizabeth Miller, Nina Bhardwaj, Gavin Thurston, Israel Lowy, Sacha Gnjatic, Myron E. Schwartz, Vladimir Jankovic, Miriam Merad. Circulating tumor DNA (ctDNA) correlates closely with tumor necrosis and relapse-free survival (RFS) in hepatocellular carcinoma (HCC) patients treated with perioperative cemiplimab [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2178.