Fine Needle Aspiration Is a Valid Tissue Source for EGFR and KRAS Molecular Testing in Lung Cancer: A Comparison Study with Core Needle Biopsy
John Stewart, Ming Guo. University of Texas MD Anderson Cancer Center, Houston, TX
Background: There is limited data in the literature comparing fine needle aspiration (FNA) biopsy with core needle biopsy (CNB) for molecular testing. In this study, we compared FNA vs. CNB for mutational analyses of EGFR and KRAS in lung cancer patients.
Design: We retrospectively reviewed the reports generated by clinical requests for EGFR and KRAS mutational analysis in lung cancer cases in the Department of Pathology from 2009 and 2010. Specimens with diagnoses of adenocarcinoma, non-small cell carcinoma-favor adenocarcinoma, or non-small cell carcinoma-NOS were included in this study. There were 210 FNAs and 509 CNBs with molecular testing results. Of these, 172 FNAs and 178 CNBs were performed in-house. FNA and CNB cases were compared with respect to specimen adequacy for testing (i.e. sufficient amount and purity of tumor to submit to the molecular lab), failure of PCR amplification (PCR failure in one or more exons/codons in the absence of a mutation detected in the others), and frequency of detected mutations. Molecular testing was performed in the Molecular Diagnostic Lab using PCR-based sequencing of EGFR exons 18-21 and KRAS codons 12, 13, and 61. Fisher's exact tests were used to assess the association between categorical variables.
Results: Similar fractions of FNAs and CNBs were deemed adequate for testing, but CNBs showed more failures in PCR amplification. Informative results therefore were obtained more often in FNAs, but not significantly (P=0.13) (Table 1). The frequencies of EGFR/KRAS mutations were similar in both groups, among all cases, and among the subset of tumors with known TTF-1 status (Table 2). Among the cases in which the TTF-1 status were known (60.5% of FNAs and 71.7% of CNBs), TTF-1 positive tumors accounted for 80.3% of FNAs and 80.6% of CNBs.
|FNA (%)||CNB (%)||P-value|
|Adequate for testing||172/197 (87.3)||178/201 (88.6)||0.76|
|DNA insufficiency||16/172 (9.3)||32/178 (18.0)||0.05|
|Informative results||156/197 (79.2)||146/201 (72.6)||0.13|
|FNA (%)||25/93 (27)||56/238 (24)||22/91 (24)||54/222 (24)|
|CNB (%)||62/237 (26)||88/412 (21)||53/241 (22)||102/428 (24)|