[1976] Testing for 29 EGFR TKI Sensitivity and Resistance Mutations in Lung Cancer Using EGFR RGQ PCR Kit

Milena Cankovic, Lisa Whiteley, Dhananjay A Chitale. Henry Ford Hospital, Detroit, MI

Background: Many studies have demonstrated the association between somatic mutations in the epidermal growth factor receptor (EGFR) gene in non-small cell lung cancer (NSCLC) and sensitivity or resistance to the EGFR tyrosine kinase inhibitors (TKIs). In this study we evaluated performance of a commercial kit (EGFR RGQ PCR, Qiagen) for detection of EGFR mutations in a variety of sample types likely to be submitted to a molecular oncology lab.
Design: Qiagen's EGFR RGQ kit detects 29 somatic mutations in the EGFR oncogene using real time PCR and Rotor Gene Q (RGQ) instrument. The kit uses Scorpions and ARMS® technologies to detect these mutations in the background of wild type genomic DNA. Sixty two confirmed NSCLC cases were tested in parallel using EGFR RGQ PCR and laboratory developed assays (LDA) EGFR exon 19 deletion/exon 21 L858R point mutation. Sample types were as follows: 42 lung biopsies/resections, 3 lymph node biopsies, 3 brain biopsies/resections, 3 liver biopsies, 1 gastric biopsy, 1 skin biopsy, 4 pleural cytology fluid cell blocks, 1 pleural cytology slide smear, 2 pericardial fluid cytology cell blocks, 1 scapula resection, 1 paraspinal mass. Manual microdissection was performed when tumor content was less than 50% of total cells (20/62 cases).
Results:

Table 1: Analytical sensitivity of the EGFR RGQ assay

Mutation	Sensitivity
T790M	10%
Deletions	1.25%
L858R	2.5%
L861Q	0.3125%
G719X	0.625%
S768I	1.25%
Insertions	2.5%

Analytical sensitivity for LDA is 5% for both the exon 19 deletion/exon 21 L858R point mutation. Exon 19 deletion was detected in 14/62 (22.6%) of cases by both methods. Exon 21 mutation was detected in 8/62 (12.9%) of cases with the LDA and 9/62 (14.5%) with the EGFR RGQ method. The EGFR RGQ method detected 3 additional mutations: one insertion, one G719X mutation, and one T790M mutation. Total cost of testing per sample is USD 48.24 for LDA and USD 628.62 for EGFR RGQ. The EGFR RGQ method has more manual steps at the set up (more tubes and pipetting) but is overall less technically challenging to run and interpret. Total run time (DNA to results) is 7 hours for LDA and 2 hrs 45 min for EGFR RGQ. The EGFR RGQ assay does not allow size determination for exon 19 deletions.
Conclusions: Although more expensive than LDA, EGFR RGQ assay offers an evaluation of 29 EGFR mutations in exons 18 to 21 currently known to be associated with sensitivity and resistance (T790M) to TKIs in NSCLC compared to only 2 mutations detected by LDA. Being able to test for more mutations at a greater sensitivity makes this assay more attractive to oncologists at our institution.
Category: Pulmonary

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 296, Tuesday Afternoon