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Lee A Albacker



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    EP1.01 - Advanced NSCLC (ID 150)

    • Event: WCLC 2019
    • Type: E-Poster Viewing in the Exhibit Hall
    • Track: Advanced NSCLC
    • Presentations: 1
    • Moderators:
    • Coordinates: 9/08/2019, 08:00 - 18:00, Exhibit Hall
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      EP1.01-108 - EGFR Exon 18 Mutations in NSCLC: Frequent Co-Occurrence of Multiple EGFR Mutations and Assessment of Cis/Trans Status (ID 2747)

      08:00 - 18:00  |  Author(s): Lee A Albacker

      • Abstract

      Background

      A subset of EGFR exon 18 (ex18) mutations including G719X are known drivers in NSCLC. However, the sensitivity profile of other ex18 mutations and frequently occurring dual ex18/ex18 and ex18/non-ex18 combinations has not been well described.

      Method

      Hybrid-capture based comprehensive genomic profiling was performed on 46,296 FFPE tissue samples from patients with NSCLC. Tumor mutational burden (TMB) was determined on 0.8-1.1 Mbp of sequenced DNA and reported as mut/Mb. Configuration was determined by analyzing sequencing reads that spanned both loci. The number of reads that harbored mutations at one or both positions was tabulated and used to infer cis or trans status. Patient ancestry was determined by single nucleotide polymorphism (SNP) microarray data, ancestry informative markers, and principal component analysis (PCA)..

      Result

      EGFR ex18 mutations (point mutations and indels) were identified in 1.1% (522/46,296) of NSCLCs. The median patient age was 67 years (range 30-96) and 67% of patients were female. This subset was also enriched for patients of East Asian descent when compared to EGFR wildtype NSCLC (17% v 3.9%; p < 0.001), similar to ex19del and L858R populations (19% and 24%, respectively). Median TMB was 4.35 mut/mb (range 0-70). Co-occurring EGFR mutations were identified in 69% (362/522) of cases, including most commonly S768I (20%, 103/522) and L858R (12%,61/522). T790M was detected in 6.1% (32/522) of ex18 cases. Multiple EGFR ex18 mutations occurred in 15% (76/522) of cases including 2 cases with 3 and a single case with 4 such mutations. The most commonly observed missense pairs were E709A/G719S (17/76) and E709A/G719A (16/76). Other combinations of E709X/G719X made up an additional 42% (32/76), with the remaining 14% of cases consisting of rare combinations (n<4 for all). All ex18 mutations in all cases (76/76) were in cis. Preliminary evidence from paired cases and assessment of mutant allele frequencies suggests that ex18 mutations found together in cis arise de novo. Results of in vitro studies to determine the sensitivity of single ex18 mutations as well as common pairs to all generations of EGFR inhibitors will be presented.

      Conclusion
      EGFR ex18 mutations co-occur at a high frequency with both ex18 and non-ex18 EGFR mutations, unlike classic EGFR mutations (L858R, ex19del). Female gender, East Asian ancestry, and low TMB were common in ex18 cases, similar to populations with classic EGFR mutations. In all cases with multiple EGFR ex18 mutations these mutations were always found to occur in cis. Further work to understand the evolution of these co-occurring EGFR mutations and to determine the best therapeutic strategy or strategies for this NSCLC patient population is warranted

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    MA03 - Clinomics and Genomics (ID 119)

    • Event: WCLC 2019
    • Type: Mini Oral Session
    • Track: Advanced NSCLC
    • Presentations: 1
    • Now Available
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      MA03.05 - BRAF Mutations Are Associated with Increased Benefit from PD1/PDL1 Blockade Compared with Other Oncogenic Drivers in Non-Small Cell Lung Cancer (Now Available) (ID 1472)

      10:30 - 12:00  |  Author(s): Lee A Albacker

      • Abstract
      • Presentation
      • Slides

      Background

      PD-1/PD-L1 immune checkpoint blockade (ICB) has revolutionized the treatment of non-small cell lung cancer (NSCLC), but only a minority of patients achieve durable clinical benefit. Although classic EGFR/ALK alterations are correlated with ICB resistance, it is unknown if patients with other molecular subtypes of NSCLC also derive poorer outcomes from ICB. We investigated if there are oncogene-driven NSCLC associated with higher response rates (RR) and progression-free survival (PFS) to ICB.

      Method

      Two independent retrospective cohorts of oncogene-driven NSCLC treated with ICB monotherapy were analyzed for clinical outcome: MD Anderson (MDACC) and Flatiron Health-Foundation Medicine Clinico-Genomic Database (FH-CGDB). PD-L1 expression (Dako 22C3 - FoundationCore) and tumor mutational burden (TMB - FoundationCore; TCGA and MSK-IMPACT – cbioportal.org) were compared across distinct molecular subtypes of NSCLC to determine differences in clinical outcome.

      Result

      Among five oncogene defined groups from the MDACC cohort, BRAF-mutant NSCLC had the highest response rate (RR) (RECIST 1.1) (P<0.01) and PFS (P<0.01) when treated with ICB (Table). These differences remained significant after adjusting for PD-L1 expression. Classic EGFR and HER-2 mutant NSCLC had the lowest RR and PFS (Table). Similar results were observed in the independent FH-CGDB cohort where BRAF-mutant NSCLC had longer real-world (rw) PFS and OS to ICB monotherapy (Table). PD-L1 expression (tumor score ≥1% and ≥50%) and TMB were higher in BRAF-mutant NSCLC compared to EGFR and HER-2 (P<0.01). BRAF V600E NSCLC had lower TMB compared to non-V600E (5.9 vs 13.7 mut/Mb, P<0.01), but both had high PD-L1 expression (≥1%: 72% vs 61%; ≥50%: 42% vs 32%).

      KRAS

      BRAF

      Classic EGFR

      EGFR exon 20

      HER2

      MDACC cohort

      Patients – N

      87

      10 (V600E 3 / non-V600E 7)

      28

      25

      15

      RR – %

      24.3

      62.5

      4.5b

      10b

      8.3

      Median PFS – mo (95% CI)

      2.76

      (2.23-3.30)

      7.37 (not estimable)a

      1.78 (1.18-2.37)

      2.73 (1.71-3.75)

      1.88 (1.63-2.12)

      FH-CGDB

      Patients – N

      503

      68 (V600E 32 / non-V600E 36)

      52

      42

      25

      Median rwPFS -

      mo (95% CI)

      3.55

      (3.15-4.24)

      6.0

      (2.89-11.6)

      2.17b

      (1.77-2.63)

      2.66b

      (2.23-5.13)

      1.87b (1.31-4.34)

      Median rwOS – mo (95% CI)

      10.28

      (8.51-12.02)

      16.07

      (8.64-NA)

      5.29b

      (3.25-17.68)

      9.89b

      (3.68-20.86)

      10.81

      (4.17-NA)

      FoundationCore cohort – N

      NA

      188 (V600E 74 / non-V600E 114)

      386

      96

      57

      TMB – mean (mut/Mb)

      NA

      10.6a

      3.7

      3.8

      5.8

      PD-L1 TPS ≥ 50% (%)

      NA

      36a

      19

      23

      16

      a: P<0.01 vs all groups; b: P<0.05 for pairwise comparison vs BRAF.
      Conclusion

      NSCLCs with BRAF mutations are associated with increased benefit from ICB when compared to tumors harboring other targetable oncogenic drivers. Oncogene driver mutations are associated with distinct patterns of TMB and PD-L1 expression. These findings highlight the importance of developing mutation-specific clinical trials in NSCLC.

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