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MA15 - Immunotherapy Prediction (ID 400)
- Event: WCLC 2016
- Type: Mini Oral Session
- Track: Chemotherapy/Targeted Therapy/Immunotherapy
- Presentations: 1
MA15.11 - Acquired Resistance Mechanisms to EGFR Kinase Inhibitors Alter PD-L1 Expression Status in Lung Cancer (ID 4652)
14:20 - 15:50 | Author(s): M.A. Melnick
Immunotherapies that target PD-1/PD-L1 exploit the primary roles of cytotoxic agents in lung cancers. However, tyrosine kinase inhibitors (TKIs) are still considered to be the first choice in lung cancer patients with EGFR mutations. Although immunotherapies may be applied as second line or later therapeutic approaches in these patients, after acquisition of resistance to EGFR-TKIs, it is unclear if acquired resistance mechanisms alter PD-L1 expression status that is employed as an important predictive biomarker for PD-1/PD-L1 targeting agents.
Lung cancer cell lines with EGFR mutations (HCC827, HCC4006, PC9, and H1975) and their isogenic descendants with acquired resistance to various EGFR-TKIs were examined in this study. The resistance mechanisms of descendants include T790M secondary mutation, MET gene amplification, epithelial to mesenchymal transition (EMT), and loss of amplified EGFR mutant allele. PD-L1 expression status was analyzed by immunohistochemistry (IHC) and immunoblotting. Effects of acquired resistance mechanisms on PD-L1 expression were also evaluated by shRNA mediated knockdown of candidate molecules, and co-localization analysis using fluorescent imaging. IFN-gamma was used to mimic immune cell attack. Published microarray data of cells with acquired resistance to EGFR-TKIs were also employed to evaluate our findings.
PD-L1 expression was upregulated in several resistant cells and correlated with EGFR activation. In addition, we found that the phosphorylation of EGFR tyrosine (Y) 992 site, but not Y845, Y1068, or Y1173, was correlated with increased expression of PD-L1. We also observed that TKI-resistant cells with marked E-cadherin downregulation (HCC4006 erlotinib resistant cells and H1975 osimertinib resistant cells), one of hallmarks of EMT, showed decreased expression of PD-L1. However, one cell line (853#10), displaying EMT-like phenotype but only slight E-cadherin downregulation, showed PD-L1 upregulation. Published microarray data from three TKI-resistant lines with EMT-like features also support the correlation of low E-cadherin and reduced PD-L1 expression. ShRNA mediated knockdown of E-cadherin decreased the expression of PD-L1 in parental cell lines. IFN-gamma treatment upregulated PD-L1 expression in both parental and in resistant cells with E-cadherin downregulation, however PD-L1 expression in resistant cells was still lower and localized mainly in the cytoplasm rather than the cell membrane.
We observed a dramatic change of PD-L1 expression status in lung cancers with EGFR mutation after acquisition of resistance to EGFR-TKIs, depending on the resistance mechanisms. These results support the importance of re-biopsy after acquisition of resistance to EGFR-TKIs, not only for the resistance mechanisms but also for the evaluation of PD-L1 expression status.
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P3.02b - Poster Session with Presenters Present (ID 494)
- Event: WCLC 2016
- Type: Poster Presenters Present
- Track: Advanced NSCLC
- Presentations: 1
- Coordinates: 12/07/2016, 14:30 - 15:45, Hall B (Poster Area)
P3.02b-052 - Afatinib with or without Cetuximab for First-Line Treatment of EGFR-Mutant NSCLC: Interim Safety Results of SWOG S1403 (ID 5798)
14:30 - 15:45 | Author(s): M.A. Melnick
Afatinib is used as first-line therapy for EGFR-mutant non-small cell lung cancer (NSCLC), however resistance invariably develops. To attempt to delay resistance and improve survival, we are conducting a randomized Phase II/III trial of afatinib plus cetuximab versus afatinib alone in treatment-naïve patients with advanced EGFR-mutant NSCLC (NCT02438722).
Previously untreated patients with EGFR exon 19 deletion or L858R point mutation are randomized to afatinib 40mg PO daily plus cetuximab 500mg/m2 IV every 2 weeks (afat/cetux) or afatinib 40mg PO daily (afat). Dose reductions are performed for grade 3-4 or intolerable or medically concerning grade 2 adverse events (AEs) per CTCAE v4.0. The Phase II primary endpoint is progression-free survival and the Phase III primary endpoint is overall survival. Here we review the safety data after enrollment of the first 53 patients.
53 patients were registered as of June 30, 2016, and safety has been assessed in 47 (23 treated with afat/cetux and 24 with afat, see Table). Grade 1-2 rash occurred in 71% of patients receiving afat/cetux and 63% of patients on afat. Grade 3 rash was noted in 22% of patients on afat/cetux. Fatigue was more common in the combination arm; all occurrences were grade 1-2. Grade 1-2 diarrhea and other gastrointestinal AEs were comparable between the two arms. There were similar numbers of dose reductions for AEs on each arm. Three patients discontinued treatment due to AEs: 2 on the afat/cetux arm due to hyperglycemia and accumulated side effects and 1 on the afat arm due to weight loss and diarrhea. Figure 1
In this randomized trial of afat/cetux versus afat, treatment was tolerable in both arms of the study. Skin toxicity appears to be worse with the combination however other AEs are similar between the two groups. Enrollment to this trial is ongoing.