P3.01-78 The Cytology Samples and Plasma Specimens were Feasible for the EGFR Molecular Testing.

Abstract

EGFR mutation detection with real-time PCR is standard method to identify eligible patients for EGFR-TKI treatments in daily routine practice. Surgically resected tissues or biopsy specimens are mainly used as the sample materials for testing. However, the biopsy samples sometimes have a certain limitation in their volume and so the cytology specimens are chosen for EGFR testing instead. Plasma has also become an option especially in EGFR-TKI resistant cases in which often have difficulties to obtain the adequate tumor yield. In this study, we evaluated the feasibilities of using cytology samples and plasma specimens for the EGFR molecular testing. Patients provided written informed consent for use of the samples were participated in this prospective research. Cytology samples were obtained from biopsy and cells were suspended into liquid-based cytology (LBC) media. Tumor contents in the samples were confirmed with Papanicolaou stained slides. Plasma samples were also collected from patients shortly before the tissue biopsy. EGFR mutations in these samples were analyzed by cobas EGFR Mutation Test v2. Also, EGFR testing result of tissue specimens of the patients corresponded were collected from the medical records measured by cobas EGFR Mutation Test v2 as reference. The feasibilities of both cytology and plasma specimen were evaluated comparing with the tissue samples. One-hundred fifty-eight patients were registered to this study. Among those patients, 77 patients with matched set of samples were enrolled to this study. EGFR mutation rates in tissue, cytology, and plasma were 37.7, 29.9 and 16.9 %, respectively. Overall agreement rate of the cytology specimens and the plasma specimens against the tissue samples were 87.0 and 75.3%, respectively. All eightT790M mutation positive cases were perfectly matched between tissue and cytology specimens. The results suggested that tissue specimen is the most suitable sample for detecting mutations. Since high specificities were confirmed in both cytology and plasma specimens, the results are reliable as long as the call is positive. Choosing cytology or plasma specimens for EGFR testing can be the considerations for the patients who have difficulties in collecting tissue samples in the real world setting.