Circulating tumor DNA outperforms circulating tumor cells for KRAS mutation detection in thoracic malignancies.
BACKGROUND
Circulating biomarkers, such as circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA), are both considered for blood-based mutation detection, but limited studies have compared them in a head-to-head manner. Using KRAS (Kirsten rat sarcoma viral oncogene homolog), we performed such a comparison in patients who underwent surgery for suspected lung cancer.


METHODS
We recruited 93 patients, including 82 with lung cancer and 11 with benign diseases of the lung. Mutations were detected in codons 12 and 13 of KRAS in DNA extracted from CTCs, plasma, and matched tumors or lung tissues with custom-designed coamplification at lower denaturation temperature (COLD)-PCR assays, high-resolution melt analysis (HRM), and commercial assays (Roche Cobas(®) KRAS mutation test and Qiagen Therascreen(®) pyrosequencing KRAS kit).


RESULTS
With the Cobas mutation test, we identified KRAS mutations in 21.3% of tumors. Mutation analysis in matched CTC DNA and ctDNA samples by COLD-PCR/HRM assay revealed mutations in 30.5% (ctDNA) and 23.2% (CTC DNA) of patients with lung cancer. Combined results of different tests revealed KRAS-positive cases for 28% of tumors. The diagnostic sensitivity and specificity of KRAS mutation detection in tumors achieved with ctDNA was 0.96 (95% CI 0.81-1.00) and 0.95 (0.85-0.99), respectively. The diagnostic test performance was lower for CTC DNA, at 0.52 (0.34-0.73) and 0.88 (0.79-0.95).


CONCLUSIONS
Our results support ctDNA as a preferential specimen type for mutation screening in thoracic malignancies vs CTC DNA, achieving greater mutation detection than either CTCs or limited amounts of tumor tissue alone.
Royal Brompton and Harefield National Health Service Foundation Trust, London, UK; National Heart and Lung Institute, Imperial College London, London, UK.
Maxim B
MB
Freidin
Royal Brompton and Harefield National Health Service Foundation Trust, London, UK; National Heart and Lung Institute, Imperial College London, London, UK.
Dasha V
DV
Freydina
Royal Brompton and Harefield National Health Service Foundation Trust, London, UK;
Maria
M
Leung
Royal Brompton and Harefield National Health Service Foundation Trust, London, UK;
Angeles
A
Montero Fernandez
Royal Brompton and Harefield National Health Service Foundation Trust, London, UK; National Heart and Lung Institute, Imperial College London, London, UK.
Andrew G
AG
Nicholson
Royal Brompton and Harefield National Health Service Foundation Trust, London, UK; National Heart and Lung Institute, Imperial College London, London, UK. e.lim@rbht.nhs.uk.
Eric
E
Lim
D000368:Aged; D004252:DNA Mutational Analysis / Q000379:methods*; D004273:DNA, Neoplasm / Q000097:blood*; D005260:Female; D006801:Humans; D008168:Lung / Q000378:metabolism / Q000473:pathology*; D008175:Lung Neoplasms / Q000235:genetics* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009360:Neoplastic Cells, Circulating / Q000473:pathology*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D016283:Proto-Oncogene Proteins p21(ras); D012680:Sensitivity and Specificity; D018631:ras Proteins / Q000235:genetics*
D004273:DNA, Neoplasm; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins