Update on the large-scale screening of ALK fusion oncogene transcripts in archival NSCLC tumor specimens using multiplexed RT-PCR assays.

Abstract

7594 Background: The ALK inhibitor crizotinib offers a new standard of care for advanced NSCLC patients with EML4-ALK fusion oncogenes. We previously reported a 4.0% frequency of EML4-ALK fusion oncogene transcripts detected in 1889 NSCLC specimens in the RGI database (Li et al., ASCO 2011). Methods: Patented single and multiplexed RT-PCR assays suitable for rapid and accurate detection of all variants of ALK fusion oncogene transcripts were used as previously described, including all 9 known EML4-ALK fusion gene transcripts and ALK RNA levels (Danenberg, ASCO 2010). The sensitivity and specificity on archival formalin-fixed, paraffin-embedded tumor specimens are 99% and 100%, respectively. We here update the detection of EML4-ALK fusion transcripts in the RGI database. Results: Between 12/2009 and 09/2011, 4750 NSCLC specimens in the RGI database were tested for the presence of ALK fusion transcripts. We found 152 (3.2%) NSCLC cases with EML4-ALK fusion positivity, including 87 (57.2%) V1, 15 (9.9%) V2, 47 (30.9%) V3, and 3 (2.0%) V5a variants. Median age (range): 61.1 (33-96). Female: 74 (49%). All EML4-ALK-positive tumors were adenocarcinomas. No EGFR or K-Ras mutation was detected in ALK fusion-positive samples. Expression of chemotherapy-related biomarkers was available from 63 (female: 31, 49%) EML4-ALK-positive cases in the database: 43 (68%) had low TS level of <2.33; 40 (63.5%) had low ERCC1 level of <1.7, and 25 (40%) had low RRM1 level of <0.97. Conclusions: This RT-PCR assay provides a tool for rapid, large-scale screening of NSCLC FFPE tissues for EML4-ALK fusion gene transcripts. The relative value of this RT-PCR assay as a companion diagnostic test for drugs targeting ALK merits evaluation in comparison with the FDA approved ALK FISH test.