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MO12 - Prognostic and Predictive Biomarkers III (ID 96)
- Event: WCLC 2013
- Type: Mini Oral Abstract Session
- Track: Medical Oncology
- Presentations: 1
MO12.02 - Association between Gene Expression Profiles and Clinical Outcome of Pemetrexed-Based Treatment in Patients with Advanced Non-Squamous Non-Small Cell Lung Cancer: Exploratory Results from a Phase II Study (ID 185)
10:30 - 12:00 | Author(s): M. Das
We report exploratory gene expression profiling data from a prospective single-arm Phase-II-study in patients with non-squamous non-small cell lung cancer (nsNSCLC) treated with pemetrexed. Main results indicated a significant association of low thymidylate-synthase (TS) expression with longer PFS and OS .
Treatment-naive nsNSCLC patients (Stage IIIB/IV) received 4 cycles of first-line pemetrexed/cisplatin; non-progressing patients continued on pemetrexed maintenance . Diagnostic tissue samples were used to assess TS expression (nucleus/cytoplasm) by immunohistochemistry (IHC, H scores), and to extract total mRNA for expression-array profiling (expression of 1,030 genes summarized from 60,000 transcripts). Cox proportional-hazard models were applied to explore the association between each gene and PFS/OS, mRNA gene expression was used both as continuous and binary (cutpoint: median) variable. Unadjusted p-values (significance level =0.01) and false discovery rates (FDR) were calculated. Genes significantly correlated with PFS/OS were further correlated with TS-protein expression (Spearman rank test). Finally, unsupervised clustering was applied to all samples with mRNA expression (n=51) for all 1,030 selected array genes and an overlapping 870-gene subset associated with adenocarcinoma (ADC, n=47) previously described .
51/70 (72.9%) biopsies were evaluable; 9 of 1,030 genes were significantly associated with PFS/OS (unadjusted p<0.01). 8/9 genes were negatively correlated with nuclear TS expression; the test was statistically significant for 5/8 genes (unadjusted p<0.01, Table 1). None of these genes has a known relationship to folate metabolism. Cluster analysis of all 51 samples based on 1,030 genes revealed no clear trend regarding PFS/OS. Cluster-analysis of 47 ADC samples identified 3 groups (n=21, 11 and 15 patients, respectively) with median (95%CI) PFS and OS of 8.1 (6.9, not estimable [NE]) and 20.3 (17.5, N.E) months; 2.4 (1.2, NE) and 4.3 (1.4, NE) months; and 4.4 (1.2, NE) and 8.3 (3.9, NE) months, respectively. Figure 1
This exploratory analysis provides insights on key genes potentially linked to low TS expression. Nine genes were significantly associated with PFS/OS; however such association cannot be differentiated as prognostic or predictive since this study is single arm. Further research would be needed to understand the relationship of these markers with clinical outcomes.  Nicolson et al, J Thorac Oncol 2013, May 29 [Epub].  Wilkerson et al, PLoS One 2012;7(5):e36530.
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