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MA14 - Immunotherapy in Advanced NSCLC: Biomarkers and Costs (ID 394)
- Event: WCLC 2016
- Type: Mini Oral Session
- Track: Advanced NSCLC
- Presentations: 1
MA14.01 - Updated Dataset Assessing Tumor Mutation Burden (TMB) as a Biomarker for Response to PD-1/PD-L1 Targeted Therapies in Lung Cancer (LC) (ID 4011)
16:00 - 17:30 | Author(s): G. Kalemkerian
Immune checkpoint inhibitors (ICPIs) nivolumab and pembrolizumab have been FDA-approved in non-small cell LC (NSCLC). Current IHC based diagnostics are challenged by assay and slide scoring issues and modest predictive value, and more robust and comprehensive biomarkers of ICPI efficacy are needed. A discovery set of 64 NSCLCs treated with ICPIs suggested that high TMB (≥15 mutations/Mb) significantly correlated with longer time on drug (Spigel et al., ASCO 2016, Abstract:9017).
Comprehensive genomic profiling (CGP) was performed during the course of clinical care. TMB was assessed as the number of somatic, coding, base substitution and indels per Mb of genome. Microsatellite instability-high (MSI-H) or stable (MSS) status was determined using a proprietary algorithm.
15,529 LCs: 66% adenocarcinoma, 1% sarcomatoid, 14% NSCLC NOS, 11% squamous, 5% small cell, and 2% large cell were assessed. TMB was similar across all lung histologies (median: 6.3, 8.1, 9.0, 9.9, 9.9, and 10.8); the median was 7.6 for all LC cases (TMB ≥15 in 24% of cases), compared to 4.5 for 80,000+ samples of diverse tumor types in the database. Of LCs assessed 0.3% were MSI-H, of which 30/31 were TMB-high; however, 24% of MSS-stable cases were also TMB-high. PD-L1 amplification and DNA repair pathway mutation (MLH1, MSH2, POLE) were found in 1.0% and 1.1% of LC cases analyzed, respectively. Tumors harboring known drivers (ALK, ROS1, EGFR, BRAF V600E, MET splice) had low TMB (median: 2.5, 3.6, 3.8, 3.8, 4.5), whereas tumors with KRAS mutation, non-V600E BRAF mutation, PD-L1 amplification, or DNA repair alterations were more likely to be TMB-high (median: 9.0, 10.8, 14.4, 21.6).
High TMB may be a predictive biomarker of response to ICPIs. Several factors including lack of a known driver, MSI-H status, PD-L1 amplification, and DNA repair mutation correlated with high TMB (P<0.0001 for all cases). However, 95% of TMB-high cases assessed were MSS and lacked both PD-L1 amplification and DNA repair mutation, and thus would likely not be selected for immunotherapy by assessment of individual genomic alterations or MSI status alone. A validation cohort of NSCLC patients treated with anti-PD-1/PD-L1 therapies including analysis of clinical outcome, TMB, genomic profile, and available clinicopathologic characteristics will be presented. CGP of LC to simultaneously determine TMB, MSI status, PD-L1 amplification, and the presence of driver alterations may provide clinically useful predictors of response to ICPI and other targeted therapies using a single platform, but prospective clinical trials are needed to confirm these observations.
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