Abstract 3363: Spatial and longitudinal tumor heterogeneity in head and neck squamous cell carcinoma patients treated with primary surgery
Authors: Marret Grégoire , Lamy Constance , Vacher Sophie , Séné Mathieu , Ahmanache Ladidi , Courtois Laura , Beiano Zakhia El , Klijanienko Jerzy , Martinat Charlotte , Servant Nicolas , Kamoun Choumouss , Chérif Linda Larbi , Bronzini Thierry , Balsat Cédric , Laes Jean-François , Prévot Aubray , Sauvage Sébastien , Lienard Maxime , Martin Emmanuel , Genin Bérengère , Badois Nathalie , Lesnik Maria , Dubray-Vautrin Antoine , Choussy Olivier , Ghanem Wahib , Taouachi Rabah , Planchon Julien Masliah , Bièche Ivan , Kamal Maud , Tourneau Christophe Le 
Published: April 2023

Abstract
Introduction: Cell-free tumor DNA (ctDNA) is an emerging biomarker in head and neck squamous cell carcinoma (HNSCC) for disease staging, patients’ recurrence risk stratification and early detection of relapse. We aimed to compare variants identified in ctDNA versus surgical tumor specimen, and to study the evolution of the mutational landscape of ctDNA over time in HNSCC.
Patients and Method: Forty-one HNSCC patients treated with curative-intent primary surgery from SCANDARE cohort (NCT03017573) were evaluated for longitudinal ctDNA-based NGS. Overall, 28 patients were treated with adjuvant (chemo)radiotherapy, and 31 experienced recurrence. Formalin-fixed paraffin-embedded tumor tissues at surgery were available for 41 patients. Serial contributive ctDNA were retrieved from all 41 patients at the date of surgery, 36 patients within 19 weeks after surgery, 20 patients at six months after surgery, and 22 patients at recurrence. Tissue DNA was personalized detected with a custom NGS panel of 571 genes (DRAGON) and ctDNA was sequenced using another personalized dedicated NGS panel including up to 15 genes (OncoFOLLOW).
Results: Most frequently mutated genes in tissue included TP53 (15.9%), FAT1 (6.7%), NOTCH1 (5.5%) and PIK3CA (4.3%) with similar allelic ratio to ctDNA at baseline surgery. Higher prevalence of KRAS and TP53 mutations was found in ctDNA at recurrence in comparison with ctDNA and tissue, respectively, at baseline surgery (KRAS: 6.3% versus 1.6% and 0.6%; TP53: 31.2% versus 21.1% and 15.9%). Additional variants in NRAS, HRAS, TP53, JAK2 and SDHA were detected in 6 patients in ctDNA at surgery and were not found in tissue, suggesting spatial intratumor heterogeneity. Twenty-three/36 patients (64%) had detected ctDNA within 19 weeks after surgery among whom, 17/23 patients (74%) had disease recurrence. Eleven/20 patients (including 10 with adjuvant treatment) had detected ctDNA at six months after surgery among whom 6 patients (55%) had disease recurrence. Fifteen/22 patients (68%) had detected ctDNA at recurrence. Emerging pathogenic variants were found in patients with detected ctDNA after surgery (n=7/23; 30%), at six months after surgery (n=1/11; 9%) and at recurrence (n=4/15; 27%).
Conclusion: Our study suggests spatial and longitudinal tumor heterogeneity and reports emerging mutations in ctDNA over time in HNSCC. Prognostic significance characterization of the ctDNA dominant clone allele frequency is ongoing.
Citation Format: Grégoire Marret, Constance Lamy, Sophie Vacher, Mathieu Séné, Ladidi Ahmanache, Laura Courtois, Zakhia El Beiano, Jerzy Klijanienko, Charlotte Martinat, Nicolas Servant, Choumouss Kamoun, Linda Larbi Chérif, Thierry Bronzini, Cédric Balsat, Jean-François Laes, Aubray Prévot, Sébastien Sauvage, Maxime Lienard, Emmanuel Martin, Bérengère Genin, Nathalie Badois, Maria Lesnik, Antoine Dubray-Vautrin, Olivier Choussy, Wahib Ghanem, Rabah Taouachi, Julien Masliah Planchon, Ivan Bièche, Maud Kamal, Christophe Le Tourneau. Spatial and longitudinal tumor heterogeneity in head and neck squamous cell carcinoma patients treated with primary surgery [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 3363.