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Poster display session

3722 - Topography of Tumor Mutational Burden (TMB) and Immune-related Genomic Alterations (GA) Across Gastrointestinal Malignancies (GIm): A Study of 22,570 Cases

Date

10 Sep 2017

Session

Poster display session

Presenters

Samuel Klempner

Citation

Annals of Oncology (2017) 28 (suppl_5): v403-v427. 10.1093/annonc/mdx376

Authors

S.J. Klempner1, G.M. Frampton2, J. Chao3, M. Bailey4, P. Stephens5, J.S. Ross6, V.A. Miller7, S.M. Ali8, A.B. Schrock5

Author affiliations

  • 1 Medical Oncology, The Angeles Clinic and Research Institute, 90025 - Los Angeles/US
  • 2 Oncology, Foundation Medicine, 02141 - Cambridge/US
  • 3 Medical Oncology, City of Hope, 91010 - Duarte/US
  • 4 Oncology, Foundation Medicine, MA 02141 - Cambridge/US
  • 5 R & D, Foundation Medicine, MA 02141 - Cambridge/US
  • 6 Pathology, Albany Medical Center, 12208 - Albany/US
  • 7 Medical Affairs, Foundation Medicine, MA 02141 - Cambridge/US
  • 8 Clinical Development, Foundation Medicine, MA 02141 - Cambridge/US
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Resources

Abstract 3722

Background

Response to immune checkpoint inhibitors (ICPIs) is mediated in part by tumor neoantigens. TMB has emerged as a predictive biomarker, but data is lacking in GIm. We examined TMB and concurrent GA across GIm to identify patient subsets for further study.

Methods

Comprehensive genomic profiling was used to determine TMB, microsatellite instability (MSI), and additional GA using previously described methods. GA were compared among anatomically defined tumor types and stratified by TMB status (mutations/DNA megabase), and those associated with response or resistance to ICPIs were compared to identify patient subsets.

Results

Median TMB was higher for tubular vs. non-tubular GIm (p = 0.032). Among the entire cohort, 3.5% and 7.4% of samples had a TMB >20 and >10, respectively. The proportion of tumors with TMB ≥10 was greatest within tubular foregut structures (esophagus, stomach, duodenum; 11.2%). MSI was observed across all anatomic subtypes (range: 0.2-6%). Overall 1.2% of cases harbored receptor tyrosine kinase (RTK) fusions; colon and biliary tumors with RTK fusions had high (11) and low (2.5) median TMB, respectively. Validated immunoresponsive GA including PD-L1 amplification and POLE mutations were mutually exclusive and enriched in tubular GI structures [esophagus (0.5%), stomach (0.8%), colon (0.9%), duodenum (1.3%) and rectum (0.9%)]. POLE mutation, but not PD-L1 amplification, correlated with high TMB (median 100 and 5.4, respectively). PIK3CA catalytic (H1047R) vs. helical (E545K) domain GA were strongly associated with high TMB (p 

Conclusions

GAs associated with increased sensitivity and/or resistance to ICPIs are observed across GI cancers. Baseline genomic profling may inform rational patient selection for immunotherapy treatment. The observation that high TMB and MSI are strongly enriched for PIK3CA H1047R, and whereas low TMB and MSS are enriched for E545K, warrants further study.

Clinical trial identification

Legal entity responsible for the study

Samuel J. Klempner

Funding

None

Disclosure

S.J. Klempner: Honoraria - Foundation Medicine, Inc Advisory/Consulting - Lilly Oncology, Pfizer, Boston Biomedical. G.M. Frampton, M. Bailey, P. Stephens, J.S. Ross, V.A. Miller, S.M. Ali, A.B. Schrock: Employment - Foundation Medicine, Inc. J. Chao: Advisory/Consulting - Lilly Oncology, Boston Biomedical Research Funding – Merck.

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