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M. Smolkin



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    MINI 08 - Prognostic/Predictive Biomarkers (ID 106)

    • Event: WCLC 2015
    • Type: Mini Oral
    • Track: Biology, Pathology, and Molecular Testing
    • Presentations: 1
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      MINI08.01 - Quantitative Mass Spectrometry Proteomics Identifies FRalpha and GARFT as Predictive Biomarkers in NSCLC Patients Treated With Pemetrexed (ID 1685)

      16:45 - 18:15  |  Author(s): M. Smolkin

      • Abstract
      • Presentation
      • Slides

      Background:
      Lung cancer remains the leading cause of cancer mortality in United States and globally. Pemetrexed combined with platinum chemotherapy is specifically indicated for treatment of non-squamous non-small cell lung cancer (non-sq NSCLC). Pemetrexed is a folate-analog metabolic inhibitor that disrupts folate-dependent processes essential for cell replication. Pemetrexed inhibits thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT), which are folate-dependent enzymes involved in the de novo biosynthesis of thymidine and purine nucleotides. Folate receptor alpha (FRalpha) is a folate/antifolate transporter protein that is overexpressed by a number of epithelial tumors. The purpose of this study is to identify proteomic biomarkers predictive of response to pemetrexed-based chemotherapy in non-sq NSCLC.

      Methods:
      Patients with advanced non-sq NSCLC who received pemetrexed-based chemotherapy at West Virginia University from 2009 to 2014 were retrospectively identified. Formalin-fixed, paraffin-embedded tumor biopsies were laser microdissected, solubilized, enzymatically digested and subjected to quantitative proteomic analysis. A multiplexed, selected reaction monitoring (SRM) mass spectrometry (MS) assay was used to determine the absolute levels of 46 different candidate proteomic markers, including those in the folate receptor pathway. The Kaplan-Meier method and log-rank test were used in statistical analysis of overall survival (OS) and progression-free survival (PFS).

      Results:
      The 74 patients included in the study had a median follow-up of 26 months, a median OS of 16.6 months (95%CI: 11.6 - 43.4), and a median PFS of 9.61 months (95%CI: 8.43, 12.98). There were 65 patients who received pemetrexed-based regimen as a first line therapy and 9 patients as subsequent salvage treatment. In a comparison between patients who survived >24 months and < 8 months, there were no significant differences between the two groups in terms of sex, age, ECOG performance status, TNM stage at diagnosis, and smoking history. Among the 37 patients with sufficient tumor specimens available for multiplexed proteomic analysis, 30 biomarkers were detected with varying levels of expression. Sixteen additional biomarkers were undetectable. TS protein expression was detected in only 2 patients. Patients whose tumors expressed low levels of GARFT protein (≤900 amol/µg; n=7) had statistically significantly longer median PFS than those whose tumors expressed high levels of GARFT (>900 amol/µg; n=30) (40.6 vs. 11.4 months; p= 0.014). Patients with high FRalpha protein expression (>1510 amol/µg, n=9) had significantly longer median PFS than those with low FRalpha expression (≤1510 amol/µg; n=28) (>50 vs. 11.4 months; p= 0.021). Moreover, the 23 patients with both high GARFT expression (>900 amol/µg) and low FRalpha expression (≤1510 amol/µg) faired considerably worse than the remainder of patients (median PFS 10.1 vs. 40.6 months; p=0.0003).

      Conclusion:
      Multiplexed mass spectrometry-based proteomics offers a feasible and promising approach for tumor biomarker profiling and quantification to predict therapeutic response. Of note, our results show that FRalpha and GARFT protein expression may be predictive of response to pemetrexed-based treatment in patients with non-sq NSCLC. Further investigation is needed to validate the utility of these biomarkers for guiding personalized treatment decisions in clinical practice.

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