Thymidylate synthase (TS) gene expression in patients with ALK positive (+) non-small cell lung cancer (NSCLC): Implications for therapy.

7582 Background: ALK+ NSCLC represents a molecular target-defined patient population highly responsive to the ALK inhibitor crizotinib. Previous reports have also suggested increased sensitivity of ALK+ NSCLC to the chemotherapeutic agent pemetrexed. Thymidylate synthase (TS) is a candidate predictive biomarker for pemetrexed activity. Here we report analysis of the Response Genetics Inc. (RGI) database for this association and implications for therapy. Methods: ALK fusion was identified by a novel RT-PCR assay (Danenberg et al: ASCO 2010). For TS, RNA from microdissected formalin-fixed paraffin-embedded tumors was analyzed as previously described, reported as the ratio of gene expression to β-actin. For reference, a TS level <2.33 is the cutpoint for sensitivity. Results: TS levels were available from 63 ALK+ patients and 1,698 ALK- control lung adenocarcinoma patients. All ALK+ patients had adenocarcinomas without EGFR or KRAS mutations. Median age: 59.0 (range 33-88), gender (male/female) 32/31 (51%/49...