Specimen Consideration for EGFR Mutatiopnal Analysis in Non-Small Cell Lung Cancer
Wei Xiong, Colin Pritchard. University of Washington, Seattle, WA
Background: Between 05/2010 and 02/2011, we tested 93 cliinical specimens for mutations in exons 18 to 22 encoding TK domain of EGFR, among which 9 cases failed in the PCR amplication. In this study, we attempted to examine the properties of speicmens that may contribute to failure. The findings will help clinicians and pathologists choose the optimal specimens for EGFR mutational study.
Design: For EGFR mutation testing in our institution, speimens were first tested for the common mutations, including exon 19 deletion by fragment analysis and L858R by melting curve analysis following PCR amplficaiton. Negative cases were subsequently submitted for sequencing of exon 18 to 22. All 93 cases were included in the study. The following information was documented, including pathological diagnosis, type of speicmen (FNA, biopsy, or resection), anatomical site, referring hospital, decalcification status, size of the specimen subject to test, tumor cell per centile, DNA yield, and EGFR mutation status. For the 9 failed cases, we also documented what stage the failure occured as well as the clinical outcomes.
Results: Among 93 cases, EGFR mutation was deteted in 24% of cases and no mutation was deteded in 67% of cases. 9 cases (9%) failed for the study due to insufficient DNA for PCR amplification. Among the failed cases, 1 case turned out to be breast cancer and was subsequently exlucded from the study. In terms of specimen type, cytology specimens had the highest failure rate. The anatomical sites significantly associated with test failure inlcuded brain and bone. The size of specimen in failed cases was significantly smaller than the one in the successful cases. All the failed cases had DNA yield <2ug while majority of successful cases had DNA yield >2 ug. The failure rate in specimens <5mm3 was 15% while the failure rate was 0 in specimen >5mm3. Interestingly, only 1 out of 5 decalcified specimens (20%). In terms of outcomes, 2 cases had additional tissue from the same procedure that were successfully tested. The remaining cases had not 2nd biopsy for EGFR testing.
Conclusions: The size of the specimen is the most important factor assoicated with failure in EGFR mutational analysis of NSCLC in our study. There is 15% failure rate if the specimen is <5mm3. If sufficient sample is obtained (>5mm3), the EGFR mutational analysis has 100% successful rate. The significance of delcalcification remains unclear in this relatvely small study.
Category: Quality Assurance
Monday, March 19, 2012 1:00 PM
Poster Session II # 281, Monday Afternoon