Molecular testing of NSCLC using a platform for rapid detection of multiple oncogenetic mutations

Introduction: Molecular testing has become the standard of care for treatment of non-small cell lung cancer. Cytologic samples are frequently the only diagnostic material obtained due to the reduced procedure-related morbidity of fine-needle aspiration. This is a report of our laboratory's experience using cytology specimens for molecular testing of lung tumors.

Materials and methods: All tumors were tested in the Molecular Diagnostics Laboratory at Vanderbilt University Medical Center using the ABI PRISM SNaPshot Multiplex Kit and a separate laboratory-developed test. The assay included testing for KRAS, BRAF, NRAS, PIK3CA, MEK1, AKT1, PTEN, and EGFR mutations. Specimens were tested using a paraffin-embedded cell block, and a percentage of tumor cells was determined to establish adequacy of the sample. Ten percent or more tumor cells was considered adequate. Eighty-five cytology specimens were referred for testing, and 12% were considered inadequate. Specimens tested included 55 adenocarcinomas, 6 squamous cell carcinomas, 5 large cell neuroendocrine carcinomas, 2 small cell carcinomas, and 7 categorized as non-small cell carcinoma, unable to further differentiate. Primary lung tumors as well as lung tumors metastatic to other tissues were tested. The samples ranged from 3 mm to 15 mm, and all but 1 sample had >10% tumor cells on initial and final hematoxylin and eosin slides.

Results: Forty-eight mutations were identified in 42 tumors: 21 KRAS, 22 EGFR, 1 BRAF, 1 NRAS, 1 PIK3CA, 1 ERBB2, and 1 MEK1. Thirty-three tumors were negative for the mutations tested.

Conclusions: The DNA yield from cytology specimens is routinely adequate for molecular mutation analysis of lung cancer.