Mutant BRAF(T1799A) can be detected in the blood of papillary thyroid carcinoma patients and correlates with disease status.
BACKGROUND
The BRAF(T1799A) transversion is the most frequent morphotype-specific somatic mutation in papillary thyroid carcinoma (PTC). The ability to detect this mutation in the circulation could aid in diagnosis and follow-up of PTC patients.


OBJECTIVE
Our objective was to develop and clinically validate a sensitive and specific assay for the detection of BRAF(T1799A) in blood samples from PTC patients.


METHODS
We developed an allele-specific real-time PCR method for the detection of BRAF(T1799A) in blood samples and studied prospectively blood samples from 193 patients with thyroid cancer (173 PTC, 20 non-PTC) attending for routine follow-up. The results of molecular testing were correlated with disease status and thyroglobulin measurements. BRAF(T1799A) status of the original tumor samples was also confirmed, where available.


RESULTS
The assay had a detection sensitivity of fewer than one heterozygote BRAF(T1799A)-carrying cell per 100,000 diploid cells, without detectable cross-reactivity between wild-type BRAF and BRAF(T1799A). Circulating BRAF(T1799A) was detected in 20 of 173 PTC patients and in none of the 20 non-PTC patients. BRAF(T1799A)-positive samples contained between one in 326 and fewer than one in 100,000 copies of BRAF(T1799A). Tissue BRAF status correlated with blood BRAF status, whereas BRAF(T1799A) positivity in blood correlated with the presence of active disease at the time of the blood draw, with eight of the 38 PTC patients with persistent/recurrent disease being positive for circulating BRAF(T1799A) (relative risk vs. circulating BRAF(T1799A)-negative, 2.55; P < 0.04).


CONCLUSIONS
BRAF(T1799A) can be detected in the blood of PTC patients with residual or metastatic disease and may provide diagnostic information.
Cradic
Kendall W
KW
Department of Laboratory Medicine and Pathology, Mayo Clinic, 200 1st Street SW, Rochester, Minnesota 55905, USA.
Milosevic
Dragana
D
Rosenberg
Anne M
AM
Erickson
Lori A
LA
McIver
Bryan
B
Grebe
Stefan K G
SK
D000293:Adolescent; D000328:Adult; D000368:Aged; D000483:Alleles; D001323:Autoantibodies / Q000097:blood; D001483:Base Sequence; D002291:Carcinoma, Papillary / Q000097:blood / Q000235:genetics* / Q000473:pathology*; D002648:Child; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D011446:Prospective Studies; D048493:Proto-Oncogene Proteins B-raf / Q000097:blood* / Q000235:genetics*; D013954:Thyroglobulin / Q000097:blood; D013960:Thyroid Function Tests; D013963:Thyroid Hormones / Q000097:blood; D013964:Thyroid Neoplasms / Q000097:blood / Q000235:genetics* / Q000473:pathology*; D013972:Thyrotropin / Q000097:blood; D055815:Young Adult
D001323:Autoantibodies; D004273:DNA, Neoplasm; D013963:Thyroid Hormones; D013972:Thyrotropin; D013954:Thyroglobulin; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf