Utility of circulating B-RAF DNA mutation in serum for monitoring melanoma patients receiving biochemotherapy.
OBJECTIVE
Somatic B-RAF gene mutation has been identified in many malignancies and detected at a high frequency in cutaneous malignant melanoma. However, the significance of the B-RAF mutation (B-RAFmt) in terms of its prognostic and predictive capabilities for treatment response or disease outcome is not known. We hypothesized that circulating serum B-RAFmt (B-RAFsmt) at V600E, detected in serum, predicts response in melanoma patients receiving concurrent biochemotherapy.


METHODS
A real-time clamp quantitative reverse transcription-PCR assay was designed to assess B-RAFsmt by peptide nucleic acid clamping and a locked nucleic acid hybrid probe. Normal (n = 18) and American Joint Committee on Cancer stage I to IV melanoma patients (n = 103) were evaluated. These included stage IV patients (n = 48) with blood drawn before and after biochemotherapy. Patients were classified as biochemotherapy responders or nonresponders. Responders (n = 24) had a complete or partial response following biochemotherapy; nonresponders (n = 24) developed progressive disease.


RESULTS
Of the 103 melanoma patients, 38 (37%) had B-RAFsmt DNA, of which 11 of 34 (32%) were stage I or II, and 27 of 69 (39%) were stage III or IV. Of the 48 biochemotherapy patients, 10 of 24 (42%) patients were positive for the B-RAFsmt in the respective responder and nonresponder groups before treatment. After biochemotherapy, B-RAFsmt was detected in only 1 of 10 patients (10%) in the responder group and 7 of 10 patients (70%) in the nonresponder group. B-RAFsmt is associated with significantly worse (P = 0.039) overall survival in patients receiving biochemotherapy.


CONCLUSIONS
These studies show the presence and utility of circulating B-RAFsmt DNA in melanoma patients.
Shinozaki
Masaru
M
Department of Molecular Oncology, Division of Surgical Oncology, John Wayne Cancer Institute at Saint John's Health Center and The Angeles Clinic and Research Institute, Santa Monica, California 90404, USA.
O'Day
Steven J
SJ
Kitago
Minoru
M
Amersi
Farin
F
Kuo
Christine
C
Kim
Joseph
J
Wang
He-Jing
HJ
Hoon
Dave S B
DS
D000970:Antineoplastic Agents / Q000627:therapeutic use; D015342:DNA Probes; D004273:DNA, Neoplasm / Q000097:blood*; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008545:Melanoma / Q000097:blood* / Q000188:drug therapy / Q000473:pathology; D008875:Middle Aged; D009154:Mutation; D011237:Predictive Value of Tests; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D012878:Skin Neoplasms / Q000097:blood* / Q000188:drug therapy / Q000473:pathology; D016896:Treatment Outcome
D000970:Antineoplastic Agents; D015342:DNA Probes; D004273:DNA, Neoplasm; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf