Rebiopsy of lung cancer patients with acquired resistance to EGFR inhibitors and enhanced detection of the T790M mutation using a locked nucleic acid-based assay.
BACKGROUND
The epidermal growth factor receptor (EGFR) mutation T790M is reported in approximately 50% of lung cancers with acquired resistance to EGFR inhibitors and is a potential prognostic and predictive biomarker. Its assessment can be challenging due to limited tissue availability and underdetection at low mutant allele levels. Here, we sought to determine the feasibility of tumor rebiopsy and to more accurately assess the prevalence of the T790M using a highly sensitive locked nucleic acid (LNA) PCR/sequencing assay. MET amplification was also analyzed.


METHODS
Patients with acquired resistance were rebiopsied and samples were studied for sensitizing EGFR mutations. Positive cases were evaluated for T790M using standard PCR-based methods and a subset were re-evaluated with an LNA-PCR/sequencing method with an analytical sensitivity of approximately 0.1%. MET amplification was assessed by FISH.


RESULTS
Of 121 patients undergoing tissue sampling, 104 (86%) were successfully analyzed for sensitizing EGFR mutations. Most failures were related to low tumor content. All patients (61/61) with matched pretreatment and resistance specimens showed concordance for the original sensitizing EGFR mutation. Standard T790M mutation analysis on 99 patients detected 51(51%) mutants. Retesting of 30 negative patients by the LNA-based method detected 11 additional mutants for an estimated prevalence of 68%. MET was amplified in 11% of cases (4/37).


CONCLUSIONS
The re-biopsy of lung cancer patients with acquired resistance is feasible and provides sufficient material for mutation analysis in most patients. Using high sensitivity methods, the T790M is detected in up to 68% of these patients.
Molecular Diagnostics Service, Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA.
Maria E
ME
Arcila
Geoffrey R
GR
Oxnard
Khedoudja
K
Nafa
Gregory J
GJ
Riely
Stephen B
SB
Solomon
Maureen F
MF
Zakowski
Mark G
MG
Kris
William
W
Pao
Vincent A
VA
Miller
Marc
M
Ladanyi
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D014408:Biomarkers, Tumor; D001706:Biopsy; D004252:DNA Mutational Analysis; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000235:genetics* / Q000378:metabolism; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008175:Lung Neoplasms / Q000235:genetics* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009841:Oligonucleotides; D016133:Polymerase Chain Reaction / Q000379:methods*; D011379:Prognosis
D014408:Biomarkers, Tumor; D009841:Oligonucleotides; C477371:locked nucleic acid; D066246:ErbB Receptors
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