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MA26 - New Therapies and Emerging Data in ALK, EGFR and ROS1 (ID 930)
- Event: WCLC 2018
- Type: Mini Oral Abstract Session
- Track: Targeted Therapy
- Presentations: 1
- Coordinates: 9/26/2018, 13:30 - 15:00, Room 201 BD
MA26.03 - Activity of Osimertinib and the Selective RET Inhibitor BLU-667 in an EGFR-Mutant Patient with Acquired RET Rearrangement (ID 14731)
13:40 - 13:45 | Author(s): Subba Digumarthy
The spectrum of acquired resistance (AR) to osimertinib is not yet fully characterized. We present a single-center cohort of osimertinib AR biopsies and results of a patient with RET-mediated AR treated with the investigational RET-specific TKI BLU-667 and osimertinib.
We assayed tissue via SNaPshot or Foundation One next-generation sequencing (NGS) and plasma via Guardant360 NGS under an IRB-approved protocol. In vitro studies assessed implications of RET fusions in EGFR-mutant cancers. We treated one patient with osimertinib/BLU-667 using an IRB and FDA-approved compassionate use protocol.
41 EGFR-mutant patients with AR to osimertinib were assessed histologically and queried by tissue NGS (n=22), plasma NGS (n=9) or both (n=10). Key AR findings: SCLC transformation (2/32 tissue); EGFR C797S (5/32 tissue, 5/19 plasma, all cis with T790M); MET amplification (7/32 tissue, 3/19 plasma); BRAF rearrangement (2/32 tissue) and CCDC6-RET rearrangement (1/32 tissue, 1/19 plasma [distinct case]).
CCDC6-RET was expressed in PC9 (EGFR del19) and MGH134 (EGFR L858R/T790M) cells, which maintained MAPK signaling and conferred resistance to osimertinib and afatinib. Inhibition of RET by BLU-667 or cabozantinib resensitized cells expressing CCDC6-RET to EGFR inhibition.
A 60-year-old woman with EGFR del19 progressed on afatinib (T790M+), then osimertinib. Tissue biopsy at osimertinib AR showed acquired CCDC6-RET (T790-wt). She began osimertinib 80mg/BLU-667 200mg daily x2 weeks, then BLU-667 was increased to 300mg daily. Her dyspnea improved within days of initiation. Scans after 8 weeks revealed a marked response with RECIST tumor shrinkage of 78% (Figure). She experienced only grade 1 toxicities of fatigue, leukopenia, hypertension, dry mouth, and elevated transaminases.
RET rearrangements are rare but recurrent in EGFR-mutant patients with AR to osimertinib. In vivo models suggest they mediate AR and this patient provides proof-of-concept that combination EGFR+RET inhibition with osimertinib/BLU-667 is a well-tolerated and effective regimen for RET-mediated AR. Further study is ongoing.
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P1.04 - Immunooncology (Not CME Accredited Session) (ID 936)
- Event: WCLC 2018
- Type: Poster Viewing in the Exhibit Hall
- Presentations: 1
- Coordinates: 9/24/2018, 16:45 - 18:00, Exhibit Hall
P1.04-21 - The Utility of PD-L1/CD8 Dual Immunohistochemistry for Prediction of Response to Immunotherapy in Non-Small Cell Lung Cancer (NSCLC) (ID 13815)
16:45 - 18:00 | Author(s): Subba Digumarthy
PD-L1 immunohistochemistry (IHC) is an important predictive biomarker for PD-(L)1 blockade in advanced non-small cell lung cancer (NSCLC); however, this assay is imperfect. The presence of CD8+ tumor infiltrating lymphocytes (TILs) may be a complimentary biomarker for response to immunotherapy. Thus, we examined the performance of PD-L1/CD8 dual IHC (dIHC) in two cohorts of NSCLC patients receiving immunotherapy.a9ded1e5ce5d75814730bb4caaf49419 Method
Patients were identified through retrospective review of medical oncology and pathology databases. The first cohort predominantly received nivolumab as a 2nd or later line treatment; tissue samples were mainly obtained at initial diagnosis. The second cohort received pembrolizumab as a first line therapy, and tissue samples were procured immediately before the initiation of immunotherapy. PD-L1/CD8 dIHC was performed on those tissue samples. Percentage of tumor cells with membranous PD-L1 expression and CD8+ stromal cells were measured, and CD8+ TILs were semi-quantitatively evaluated. The quantities of CD8+ T cells were dichotomized with appropriate cut-offs.4c3880bb027f159e801041b1021e88e8 Result
Eighty-four patients were identified, including 60 in the Nivolumab cohort (NC) and 24 in the Pembrolizumab cohort (PC). In the NC, PD-L1 expression ≥1% was marginally associated with improved progression-free survival (PFS, p=0.09), and an increased rate of response (p=0.08). CD8+ TILs and stromal cells did not correlate with outcome. However, a subset of PD-L1-positive patients who showed abundant CD8+ TILs and stromal cells had significantly reduced PFS (p=0.04). In the PC cohort, all cases chosen exhibited PD-L1 expression in ≥50% of tumor cells. Increased CD8+ TILs were correlated with improved PFS, (p=0.0194), and an increase in both CD8+ TILs and stromal cells was also associated with improved PFS (p= 0.0238).8eea62084ca7e541d918e823422bd82e Conclusion
Although limited by small sample size, this study suggests that PD-L1/CD8 dIHC improves the prediction of response to the PD-1/PD-L1 blockade in advanced NSCLC patients when it is performed on tissue samples obtained immediately before the initiation of the blockade as first-line therapy . However, for the 2nd or later line of treatment, dIHC on archival tissue samples obtained before initial therapy provides a useful but less clear picture of the tumor immune microenvironment. Reduced PFS seen in patients with PD-L1 expression and abundant CD8+ TILs and stromal cells may be due to T-cell exhaustion after the chemotherapy before the PD-1/PD-L1 blockade. These findings suggest that PD-L1/CD8 dIHC may be useful for treatment response stratification in advanced lung cancer patients.6f8b794f3246b0c1e1780bb4d4d5dc53