Accuracy of Cytology Specimen and Needle Core Biopsies for Detection of KRAS Mutation in Non-Small Cell Carcinoma: Comparison With Resection Specimen

BACKGROUND: Recent studies have shown that KRAS mutations are negative predictors of benefit from both adjuvant chemotherapy and anti-EGFR directed therapies for non-small cell lung carcinoma (NSCLC). Needle core biopsy, cytology specimen and resected tissue have all been used for KRAS mutational analysis of malignant lung tumors. However, studies validating the correlation between needle core biopsy/cytology specimen and resected tissue, histologic reference standard for KRAS mutational analysis are lacking. We retrospectively compared the KRAS mutation detection on cytology specimen or needle core biopsy with corresponding resected malignant neoplasm of lung, the histologic reference standard for mutational analysis. METHOD: Twenty-seven samples including 8 cell blocks, 9 cytology smears and 10 needle core biopsies, and corresponding 22 resected malignant tumor of lung were correlated for KRAS mutational analysis. In cases where cell block material did not correspond with results on resected specimen, cytology smears of corresponding cases were microdissected for isolation of DNA. RESULTS: The needle core biopsy specimens and the corresponding surgical resections showed 100% concordant results for KRAS mutational analysis. KRAS mutation was detected in 4 out of 8 cell blocks, compared to 7 out of 8 corresponding surgical resections. Low cellularity (2 cases) and failure to retrieve DNA (1case) resulted in lack of correlation in 3 cases with cell blocks. However, cytology smears in these 3 cases confirmed the KRAS mutation noted in corresponding surgical resections. Overall concordance between cytology smears and corresponding surgical resections was 89% (8 of 9 cases). KRAS mutation was detected in 1 of the 9 cytology smears and was lacking in corresponding surgically resection. CONCLUSION: Cytology specimen and needle core biopsies provide adequate material for KRAS mutational analysis. Excellent mutational analysis concordance between cytology specimen/needle core biopsies and resected tumor suggests that predictive marker based therapeutic decision need not shift to more invasive surgical procedures.