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ORAL 02 - PD1 Axis Immunotherapy 2 (ID 87)
- Event: WCLC 2015
- Type: Oral Session
- Track: Treatment of Advanced Diseases - NSCLC
- Presentations: 1
ORAL02.06 - Evaluation of PD-L1 Expression in Metachronous Tumor Samples and FDG-PET as a Predictive Biomarker in Ph2 Study (FIR) of Atezolizumab (MPDL3280A) (ID 2207)
10:45 - 12:15 | Author(s): M. Gordon
PD-L1 expression on tumor-infiltrating immune cells (IC) and/or tumor cells (TC) can inhibit antitumor immunity. Atezolizumab (MPDL3280A) is an anti-PDL1 antibody that has shown efficacy across multiple tumor types. The efficacy and safety of atezolizumab in the Phase 2 FIR study has been reported previously (Spigel et al, ASCO 2015). Efficacy appeared to correlate with PD-L1 expression on IC and/or TC, with higher ORRs observed in patients with the highest expression of PD-L1, indicating that PD-L1 may be a predictive biomarker for response to atezolizumab. FIR was also designed to address questions of potential heterogeneity and changes in tumor PD-L1 expression in metachronous tissue samples, as well as the utility of using FDG-PET as a biomarker for response to atezolizumab in PD-L1–selected patients with NSCLC.
FIR is a 3-cohort, single-arm, Phase 2 study of atezolizumab in PD-L1–selected patients with stage IIIB/IV NSCLC. Cohort 1 included chemo-naive patients, Cohort 2 included ≥ 2L patients without a history of brain metastases, and Cohort 3 included ≥ 2L patients with asymptomatic treated brain metastases. PD-L1 expression was centrally assessed by immunohistochemistry (IHC) using the SP142 antibody assay in archival and/or fresh tumor biopsies or resections and scored as IC0, 1, 2 or 3 and TC0, 1, 2 or 3. Patients with PD-L1 IC2/3 or TC2/3 tumors were enrolled and received 1200 mg atezolizumab IV every 3 weeks (last patient entered Jun 27, 2014). Responses were measured by RECIST v1.1, modified RECIST and FDG-PET using EORTC criteria. Exploratory objectives included the evaluation of potential predictive biomarkers, including the comparison of PD-L1 expression in matched archival and fresh tumor specimens, as well as the utility of FDG-PET in assessing response to immune checkpoint blockade.
From 1009 screened patients, 95 paired archival and fresh tumor samples were obtained. In these samples, the agreement of PD-L1 expression between fresh and archival tissue at the TC3 or IC3 cutoff was 88% when the same type of tissue procurement method was used (resection or biopsy), compared with 65% when different methods of procurement were used. To date, FDG-PET response has been centrally assessed in 71 of the 138 patients enrolled in FIR. Patients with metabolic response by EORTC criteria on 6-week scans had a higher ORR per RECIST v1.1 (72% [13/18]) than metabolic non-responders (ORR 4% [2/53]).
There was a high agreement in TC3 or IC3 PD-L1 expression between archival and fresh tumor specimens. This work demonstrates that intra-patient heterogeneity in PD-L1 expression is low in metachronous tissues, indicating various types of tumor samples, including fresh or archival, can be reliably used to assess PD-L1 expression. In addition, FDG-PET has potential as an early on-treatment measure of response to atezolizumab. Further analyses will be presented. (NCT01846416)
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