Comparative evaluation of the new FDA approved THxID™-BRAF test with high resolution melting and sanger sequencing

Since patients diagnosed with BRAF V600E and V600K mutated advanced melanoma show response to treatment with MAP kinase inhibitors, several sensitive methods have been developed to determine the V600 allele status of melanoma patients.

Marchant et al BMC Cancer 2014, 14:519 http://www.biomedcentral.com/1471-2407/14/519 TECHNICAL ADVANCE Open Access Comparative evaluation of the new FDA approved THxID™-BRAF test with high resolution melting and sanger sequencing Julie Marchant1, Alain Mange1,2, Marion Larrieux1, Valérie Costes1,2† and Jérôme Solassol1,2*† Abstract Background: Since patients diagnosed with BRAF V600E and V600K mutated advanced melanoma show response to treatment with MAP kinase inhibitors, several sensitive methods have been developed to determine the V600 allele status of melanoma patients Vemurafenib (Zelboraf) and dabrafenib (Tafinlar) are specific BRAF V600 inhibitors recently approved by the US FDA as single agent treatments for unresectable or metastatic melanoma in patients with the BRAF V600 mutation Methods: We assessed the new CE THxID™-BRAF diagnostic test, which is also FDA-approved as a companion diagnostic test in the US under a specific reference and compared the results of this assay with both High Resolution Melting (HRM) and Sanger sequencing in 113 melanoma FFPE samples Results: Invalid results were observed in 0/113 specimen with HRM, 5/113 (4.4%) with Sanger sequencing, and 1/113 (0.9%) with the THxID™-BRAF test Positive percentage agreement (PPA) was 93.5% (95% CI 82.5 - 97.8) for V600E and V600K mutations combined for the THxID™-BRAF test and HRM, and negative percentage agreement (NPA) was 100.0% (95% CI 94.5 - 100.0) For the THxID™-BRAF test and Sanger, PPA was 100.0% (95% CI 92.1 - 100.0) and NPA 100.0% (95% CI 94.2 - 100.0) One V600E sample identified by THxID™-BRAF test was detected as wild-type by HRM and uninterpretable by Sanger All V600K (n = 3) were detected using the different approaches Finally, percent agreement values were not significantly different when using punches (n = 77) vs slides (n = 36) or depending on samples characteristics such as pigmentation, necrosis, and tumor content Conclusions: This study demonstrated the high agreement between the FDA approved THxID™-BRAF assay, HRM, and Sanger sequencing It has also highlighted the potential of THxID™-BRAF to be applied to a broader range of sample types than claimed in the current “instructions for use”, an extension that would require the ad hoc validation and approval Keywords: Melanoma, BRAF, Detection, V600 mutations Background Melanoma is a cutaneous malignant tumor developed from melanocytes Melanoma is expected to be diagnosed in 76,690 persons in the United States, and 9,480 patients will die of the disease in 2013 [1] As long as the disease stays localized, cutaneous melanoma presents a favourable prognosis Indeed, the therapeutic coverage of the earlystage melanoma (stage I and II of the American Joint * Correspondence: j-solassol@chu-montpellier.fr † Equal contributors Department of Biopathology, Center Hospital University, Avenue du Doyen Giraud, 34298 Montpellier Cedex 5, France University of Montpellier I, Montpellier, France Committee on Cancer -AJCC) is essentially surgical with a cure rate that approaches 90% [2] However, a substantial minority will develop disseminated disease (stage IV) The prognosis for patients with stage IV melanoma has historically been poor, with median survival less than year and a 5-year overall survival rate of