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Steven F. Powell



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    OA04 - Immuno Combinations and the Role of TMB (ID 126)

    • Event: WCLC 2019
    • Type: Oral Session
    • Track: Immuno-oncology
    • Presentations: 1
    • Now Available
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      OA04.05 - KEYNOTE-021: TMB and Outcomes for Carboplatin and Pemetrexed With or Without Pembrolizumab for Nonsquamous NSCLC (Now Available) (ID 2630)

      15:15 - 16:45  |  Author(s): Steven F. Powell

      • Abstract
      • Presentation
      • Slides

      Background

      KEYNOTE-021 cohort C was the first study to show antitumor activity for pembrolizumab plus platinum-based chemotherapy in previously untreated advanced nonsquamous NSCLC; the combination significantly improved efficacy vs platinum-based chemotherapy alone in cohort G. We explored the relationship between TMB and outcomes in KEYNOTE-021 cohorts C and G.

      Method

      All patients in cohort C received pembrolizumab plus carboplatin and pemetrexed. Patients in cohort G were randomized 1:1 to pembrolizumab plus carboplatin and pemetrexed or carboplatin and pemetrexed alone. TMB was determined by whole-exome sequencing of tumor and matched normal DNA. Association of TMB (continuous, log10 transformed) with outcomes for pembrolizumab plus chemotherapy and chemotherapy alone were assessed using logistic regression for ORR and Cox proportional hazards models for PFS and OS adjusted for ECOG PS; statistical significance was determined at the 0.05 level without multiplicity adjustment. The correlation of TMB (continuous, log10­ transformed) with PD-L1 TPS (square root scale) was assessed in the combined population. The clinical utility of TMB for ORR using a prespecified TMB cutpoint of 175 Mut/exome (~13 Mut/Mb by FoundationOne CDx) was assessed for pembrolizumab + chemotherapy.

      Result

      TMB data were evaluable for 70 patients: 12/24 (50.0%) in cohort C, 32/60 (53.3%) in the cohort G pembrolizumab plus chemotherapy arm, and 26/63 (41.3%) in the cohort G chemotherapy only arm; median age was 65 years (IQR, 57-70) and 61% were female. Baseline characteristics were generally similar in the TMB-evaluable and total populations. TMB as a continuous variable was not significantly associated with ORR, PFS, or OS for pembrolizumab plus chemotherapy (one-sided P = 0.180, 0.187 and 0.081, respectively) or chemotherapy alone (one-sided P = 0.861, 0.795 and 0.763, respectively). There was no significant correlation between TMB and TPS (r=0.12, P=0.34). ORR (95% CI) in patients treated with pembrolizumab plus chemotherapy was 60.8% (38.5-80.3) in the 23 patients with TMB <175 and 71.4% (47.8-88.7) in the 21 patients with TMB ≥175.

      Conclusion

      In this exploratory analysis, TMB was not significantly associated with efficacy of pembrolizumab plus carboplatin and pemetrexed or carboplatin and pemetrexed alone as first-line therapy for metastatic nonsquamous NSCLC. TMB was not significantly correlated with PD-L1 expression. Among pembrolizumab plus chemotherapy-treated patients, ORR was high in both the TMB low and high subgroups. Sample size is a limitation of this study; exploration in larger datasets is required to understand any differential efficacy of pembrolizumab plus chemotherapy vs chemotherapy alone based on TMB status.

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