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A. Chiang



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    MA16 - Novel Strategies in Targeted Therapy (ID 407)

    • Event: WCLC 2016
    • Type: Mini Oral Session
    • Track: Chemotherapy/Targeted Therapy/Immunotherapy
    • Presentations: 1
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      MA16.02 - Mutational Landscape of TKI Naïve and Resistant EGFR Mutant Lung Adenocarcinomas (ID 5777)

      14:20 - 15:50  |  Author(s): A. Chiang

      • Abstract
      • Presentation
      • Slides

      Background:
      The identification and development of tyrosine kinase inhibitors (TKIs) targeting the epidermal growth factor receptor (EGFR) have revolutionized and greatly improved the treatment of EGFR-mutant non-small cell lung cancer (NSCLC). Unfortunately, acquired resistance (AR) to these agents remains a major clinical problem hindering durable responses. Although significant work has been done to identify particular mechanisms of acquired resistance, little is known regarding the global mutational landscape of EGFR mutant tumors before therapy or at the manifestation of acquired resistance.

      Methods:
      Using specimens obtained in the IRB approved, Yale Lung Rebiopsy program, we completed whole exome sequencing of 15 EGFR mutant tumors with paired tissue obtained pre-treatment and at the time of AR to EGFR TKIs. An additional 5 unpaired AR samples were also analyzed. The mutational burden and copy number profile of the specimens were studied.

      Results:
      We found that the mutational burden of pre-treatment EGFR mutant tumors varies widely between tumors. TKI treatment, however, does not significantly alter the overall or non-synonymous mutation load at AR. Interestingly, EGFR[L858R]tumors had a significantly higher mutation burden at acquired resistance to EGFR TKIs than EGFR[Δ19] tumors. The higher mutation burden in EGFR[L858R] tumors compared to those harboring EGFR[Δ19 ]mutations was further confirmed through analysis of TCGA data. Recurrently altered genes shared in the pre- and AR specimens include TP53, EGFR and AKT1. Alterations in EGFR (T790M), MYCBP2, WHSC1L1, AXL, MET, HGF, MYC and NTRK1 were found at exclusively at AR.

      Conclusion:
      Collectively, these data provide valuable insight into the mutational landscape of EGFR mutant NSCLCs as they evolve on TKIs and identify potential resistance candidate genes for further investigation.

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    P3.02c - Poster Session with Presenters Present (ID 472)

    • Event: WCLC 2016
    • Type: Poster Presenters Present
    • Track: Advanced NSCLC
    • Presentations: 2
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      P3.02c-048 - A Phase I/II Trial Evaluating the Combination of Stereotactic Body Radiotherapy and Pembrolizumab in Metastatic NSCLC (ID 5249)

      14:30 - 15:45  |  Author(s): A. Chiang

      • Abstract

      Background:
      Immune checkpoint inhibitors are taking on a growing role in the treatment of patients with metastatic NSCLC. Pre-clinical evidence suggests that radiotherapy may increase the frequency, or enhance the strength of the host anti-cancer immune response. We report the preliminary results of an ongoing phase I/II trial combining stereotactic body radiotherapy (SBRT) and the anti-PD-1 antibody pembrolizumab in patients with metastatic NSCLC.

      Methods:
      Eligible patients are those with metastatic NSCLC who have received no prior immune-directed therapy, and have at least 2 sites of measurable disease as per RECIST 1.1. PD-L1 expression is not required for study entry. All patients are treated with pembrolizumab at 200 mg every 3 weeks until development of progressive disease by immune-related RECIST criteria (irPD). After irPD, patients receive SBRT to a single site of disease and continue pembrolizumab. The primary endpoint is safety and tolerability. Secondary endpoints include the pre- and post-SBRT overall response rate.

      Results:
      27 patients with advanced NSCLC have enrolled and started trial therapy. The overall response rate (irPR and irCR) to the initial course of pembrolizumab is 35%. To date, 13 patients have had irPD: 5 were not eligible for SBRT and stopped study treatment (2 developed new brain metastases, 3 had decline in PS), and 8 patients received SBRT to a single site of disease (6 thoracic, 1 adrenal, 1 vertebral) and continued pembrolizumab. 5 of these patients are evaluable for post-SBRT response: 1 patient had confirmed irPD, 4 have irSD and continue pembrolizumab post-SBRT at a median duration of 3 months (range 1 to 5 months). 2 of the 4 patients with irSD have had > 20% decrease in the sum of diameters of their unirradiated targets, since SBRT. Regarding adverse events, in the pre-SBRT phase 6 of 27 patients (22%) developed grade 3 treatment-related toxicity (2 colitis, hepatitis, pneumonitis, hypothyroidism, conjunctivitis). In the SBRT and post-SBRT phases, there have been no grade 2 or greater treatment-related events.

      Conclusion:
      The addition of SBRT to pembrolizumab has not resulted in an increase in treatment-related toxicity. Several patients who had serially confirmed irPD to pembrolizumab monotherapy underwent SBRT and now have irSD, with some evidence of tumor regression. Updated results will be presented.

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      P3.02c-088 - Acquired Resistance to Programmed Death-1 Axis Inhibitors in Non-Small Cell Lung Cancer (NSCLC) (ID 5625)

      14:30 - 15:45  |  Author(s): A. Chiang

      • Abstract

      Background:
      Programmed death-1 (PD-1) axis inhibitors are increasingly being used to treat patients with advanced NSCLC. Despite durable responses relative to chemotherapy, resistance to such therapy develops in the majority of responders, with median duration of response from 12-17 months. Mechanisms of acquired resistance (AR) to PD-1 axis inhibitors are poorly understood.

      Methods:
      Patients with advanced NSCLC and acquired resistance (AR) to PD-1 axis inhibitor therapy were enrolled to an IRB approved repeat biopsy protocol allowing collection of clinical data, archived and fresh tumor tissue, and blood for analysis. Molecular analyses including whole exome sequencing of pre- and post-treatment tumor specimens were performed.

      Results:
      Twelve cases were available for analysis (table 1). Eight and two patients developed resistance limited to lymph nodes (LNs) and adrenal gland respectively. The two remaining patients experienced tumor progression in LNs with other sites of tumor growth (one in liver, one in lung). Nine patients had sufficient archived pre- PD-1 axis inhibitor tumor tissue for analysis/ comparison, leaving three unpaired cases. Genomic analysis of tumor specimens identified two patients with acquired tumor beta-2-microglobulin (B2M) defects at resistance. A patient derived xenograft generated from one of the resistance samples (patient #6) lacked production of B2M protein and did not express surface MHC-1. Additional analyses including immunophenotyping with multiplexed quantitative immunofluorescence on these and other patient samples are ongoing. Figure 1



      Conclusion:
      Lymph nodes may be a particularly susceptible area to AR to PD-1 axis inhibitors. Defects in B2M leading to loss of tumor MHC-1 presentation may represent a unique mechanism of AR to immune checkpoint inhibitors. Further studies to determine the frequency of defects in antigen presentation machinery in tumors with resistance to PD1 axis inhibitors are warranted.