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  MA19 - Genomic Markers of IO Response (ID 922)

  • Event: WCLC 2018
  • Type: Mini Oral Abstract Session
  • Track: Immunooncology
  • Presentations: 1
  • Moderators:
  • Coordinates: 9/25/2018, 15:15 - 16:45, Room 201 BD

  • 26112

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    MA19.01 - Efficacy and Genomic Correlates of Response to Anti-PD1/PD-L1 Blockade in Non-Small Cell Lung Cancers Harboring Targetable Oncogenes (ID 12921)

    15:15 - 15:20  |  Presenting Author(s): Natalie Vokes
    • Abstract
    • Presentation
    • Slides

    Background
    

    Immune-checkpoint inhibitors (ICIs) are associated with improved outcomes in a subset of patients with advanced non-small cell lung cancer (NSCLC). NSCLCs with targetable oncogenes are thought to be less responsive to ICI therapy, possibly due to association with never smoking status and reduced tumor mutational burden (TMB), but this has not been comprehensively characterized. We evaluated the responsiveness of NSCLCs with targetable oncogenes to ICIs, and if mutation type or TMB influence response.

    a9ded1e5ce5d75814730bb4caaf49419 Method
    

    Clinicopathologic, radiographic response, and sequencing data for patients with advanced NSCLC treated with ICI therapy was acquired from two separate cohorts (DFCI Oncopanel, n=296; MSKCC MSK-IMPACT, n=202). Durable clinical benefit (DCB) was defined as responsive/stable disease > 6 months. Samples with activating mutations in EGFR, ALK, ROS, BRAF, MET, and RET were identified. TMB was calculated as the sum of nonsynonymous mutations divided by the coding region captured in each panel. Objective response rates (ORR), DCB, and TMB were compared in targetable oncogene positive (TOP) vs oncogene negative (TON) patients. TMB was considered within each cohort to avoid confounding for differences in NGS panel technique.

    4c3880bb027f159e801041b1021e88e8 Result
    

    Targetable oncogenes were identified in 16% (82/498) of patients; 44(9%) EGFR, 15(3%) MET exon 14 splice site mutated, 8(2%) BRAF V600E, 6(1%) ROS1 rearranged, 5(1%) ALK rearranged, and 4(1%) RET re-arranged. Response to ICIs was similar in TOP vs TON patients, with ORR of 18% and 20%, and median PFS of 2.7 vs 2.8 months in TOP vs TON patients respectively. Among TOP patients, response rates differed by mutation type; ORR rate was 11%(5/44) in EGFR mutated, 40%(6/15) in MET mutated, 25%(2/8) in BRAF mutated, 33%(2/6) in ROS1 rearranged, and 0% in RET and ALK rearranged cancers (0/4, 0/5 respectively). Compared to WT, TMB was lower in TOP tumors (OncoPanel median 9vs11, p=0.0064; IMPACT median 4vs8, p=2.25e-06). TMB did not correlate with objective response or DCB in TOP tumors when considered collectively or by mutation type (OncoPanel median TMB 10vs8 in DCB vs NDB, p=0.52; IMPACT median TMB 3vs5 in DCB vs NDB, p=0.31)(Mann-Whitney U for all).

    8eea62084ca7e541d918e823422bd82e Conclusion
    

    Despite lower TMB in oncogene positive NSCLC, these patients still derive clinical benefit from ICIs. ICI responsiveness is likely mutation specific, and is most pronounced in MET and BRAF mutated cancers. Among targetable oncogene positive NSCLC, TMB did not distinguish benefit. Taken together, low TMB in the presence of oncogenic driver mutations should not preclude ICI therapy.

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