Tumor mutational burden assessment in non-small-cell lung cancer samples: results from the TMB<sup>2</sup> harmonization project comparing three NGS panels
Javier Ramos‐Paradas, Susana Hernández-Prieto, David Lora, Elena Eyre, Aranzazú Rosado, Tamara Caniego-Casas, Nuria Carrizo, Ana B. Enguita, María Teresa Muñoz-Jimenez, Borja Rodriguez, Urbicio Perez-Gonzalez, David Gómez-Sánchez, Irene Ferrer, Santiago Ponce Aix, Ángel Nuñez-Buiza, Pilar Garrido, José Palacios, Fernando López‐Ríos, Eva M. Garrido‐Martín, Luis Paz‐Ares
Abstract
BACKGROUND: Tumor mutational burden (TMB) is a recently proposed predictive biomarker for immunotherapy in solid tumors, including non-small cell lung cancer (NSCLC). Available assays for TMB determination differ in horizontal coverage, gene content and algorithms, leading to discrepancies in results, impacting patient selection. A harmonization study of TMB assessment with available assays in a cohort of patients with NSCLC is urgently needed. METHODS: We evaluated the TMB assessment obtained with two marketed next generation sequencing panels: TruSight Oncology 500 (TSO500) and Oncomine Tumor Mutation Load (OTML) versus a reference assay (Foundation One, FO) in 96 NSCLC samples. Additionally, we studied the level of agreement among the three methods with respect to PD-L1 expression in tumors, checked the level of different immune infiltrates versus TMB, and performed an inter-laboratory reproducibility study. Finally, adjusted cut-off values were determined. RESULTS: 55), and 0.861 (TSO500-FO) and 0.722 (OTML-FO) in tumors with PD-L1≥1% (N=41). Inter-laboratory reproducibility analyses showed higher reproducibility with TSO500. No significant differences were found in terms of immune infiltration versus TMB. Adjusted cut-off values corresponding to 10 muts/Mb with FO needed to be lowered to 7.847 muts/Mb (TSO500) and 8.380 muts/Mb (OTML) to ensure a sensitivity >88%. With these cut-offs, the positive predictive value was 78.57% (95% CI 67.82 to 89.32) and the negative predictive value was 87.50% (95% CI 77.25 to 97.75) for TSO500, while for OTML they were 73.33% (95% CI 62.14 to 84.52) and 86.11% (95% CI 74.81 to 97.41), respectively. CONCLUSIONS: Both panels exhibited robust analytical performances for TMB assessment, with stronger concordances in patients with negative PD-L1 expression. TSO500 showed a higher inter-laboratory reproducibility. The cut-offs for each assay were lowered to optimal overlap with FO.