[387] Validation of EGFR Testing on FNA Cytology and Core Biopsy Samples on the Qiagen Rotor-Gene System

Renu Khode, Douglas Larsen, Scarlet Walker, Brianne Culbreath, Shane Parish, Kimberly Walker, Lubna Sayage-Rabie, Robert Beissner, Arundhati Rao. Scott & White Hospital, Temple, TX; Propath Pathology, Dallas, TX

Background: Epidermal growth factor receptor (EGFR) mutation detection in pulmonary adenocarcinoma is of increasing importance for determination of appropriate EGFR directed therapy. If valid results can be obtained on small biopsy or fine needle aspiration samples, it will be extremely valuable for further treatment. Few comparative studies have been performed on different sample types. This study presents an optimization for FNA and surgical samples on the Qiagen Rotor-Gene and the PyroMark Q24 platforms and to compare the results on both FNA and surgical specimens.
Design: Surgical specimens and cytology cell blocks were used as formalin fixed tissue (FFPE) and compared to cytology smears obtained from FNA and pleural fluids. Laser capture microscopy was used to enrich for tumor in FFPE and cell block samples and DNA was extracted. Semiquantitative measurement of mutations in exons 18-21 on the PyroMark Q24 was compared with the qualitative measurement of mutations in exons 18-21 on the Rotor-Gene instrument which utilizes ARMS and Scorpions technology.
Results: 54 formalin fixed biopsy, lung resection specimens, FNA and cytology cell blocks (FFPE) and 43 air dried direct smears were used. This data was collected from 90 patients, 16 of who had matched cytology and surgical pathology specimens. DNA extracted from smears ranged from 0.11-244.18 ng/ul and from FFPE samples ranged from 5.22-127 ng/ul. Number of cell groups on the cytology samples ranged from 1-15. The PyroMark Q24 which has a high specificity and sensitivity with 5% mutation cut-off limit was used as the standard against which the Rotor-Gene results were compared.

Sensitivity and Specificity on the RotorGene

CYTOLOGY SMEARS	PyroMark Q24
Rotor-Gene	Positive	Negative
Positive	2	1
Negative	4	36
	Sensitivity=33%	Specificity=97%
FFPE	PyroMark Q24
Rotor-Gene	Positive	Negative
Positive	8	1
Negative	7	32
	Sensitivity=47%	Specificity=97%
Invalid (9)

Results on air dried smears were compared to FFPE (using PyroMark Q24 results only). 6/43 cases of cytology and 17/54 cases of FFPE were positive. 15/16 matched smear and FFPE cases showed identical results.
Conclusions: Direct extraction and analysis of EGFR mutations from cytology smears is a convenient and robust method for FNA obtained samples. This validation allows for collection of additional smears on site during FNA procedures, and substantially decreases the time it would take to perform the testing on the final resection specimen. Based on our preliminary data, the PyroMark Q24 platform is more sensitive than the Rotor-Gene platform.
Category: Cytopathology

Tuesday, March 20, 2012 11:30 AM

Platform Session: Section F, Tuesday Morning