BRAF Mutation Testing
The BRAF gene provides instructions for making a protein that helps transmit chemical signals from outside the cell to the cell’s nucleus.
This protein is part of a signaling pathway known as the RAS/MAPK pathway, which controls several important cell functions. Specifically, the RAS/MAPK pathway regulates the growth and division (proliferation) of cells, the process by which cells mature to carry out specific functions (differentiation), cell movement (migration), and the self-destruction of cells (apoptosis).
The BRAF Mutation and Cancer
Mutant BRAF has been implicated in the pathogenesis of several cancers, including melanoma, non-small cell lung cancer, colorectal cancer, papillary thyroid cancer, and ovarian cancer. Mutant BRAF has also been observed in glioma and gastrointestinal stromal tumor (GIST) as well as inflammatory conditions like Erdheim-Chester disease. The frequency of BRAF mutations varies widely, from more than 50% in melanomas, to 1–4% in lung cancers and approximately 5-10% in colorectal cancer.Oncotarget. 2014 Dec; 5(23): 11752–11777.
Approximately 40-60%Solit DB, Rosen N. Resistance to BRAF inhibition in melanomas. N Engl J Med. 2011 Feb 24. 364(8):772-4. [Medline].Huang T, Zhuge J, Zhang WW. Sensitive detection of BRAF V600E mutation by Amplification Refractory Mutation System (ARMS)-PCR. Biomark Res. 2013 Jan 16. 1(1):3. [Medline]. of melanomas contain a mutation in the gene that encodes BRAF that leads to constitutive activation of downstream signaling in the MAP kinase pathway. In 80-90% of these cases, the activating mutation consists of the substitution of glutamic acid for valine at amino acid 600 (V600E)Solit DB, Rosen N. Resistance to BRAF inhibition in melanomas. N Engl J Med. 2011 Feb 24. 364(8):772-4. [Medline].Huang T, Zhuge J, Zhang WW. Sensitive detection of BRAF V600E mutation by Amplification Refractory Mutation System (ARMS)-PCR. Biomark Res. 2013 Jan 16. 1(1):3. [Medline].
Melanoma accounts for 4%Jemal A, Siegel R, Xu J, Ward E. Cancer statistics, 2010. CA Cancer J Clin. 2010 Sep-Oct. 60(5):277-300 [Medline]. of incident cancers and its mortality rate is increasing.Surgical excision remains the treatment of choice for early disease, and adjuvant therapy with interferon alfa has shown benefit in some stage II and III cases. However, advanced melanoma is an aggressive disease for which there are few therapies, and which portends a poor prognosis.
A targeted therapy approach allows the classification of melanoma into different “subtypes” based on the genetic profile of the tumor. This facilitates personalized treatment as patients receive drugs based on the unique genetic profile, or subtype, of their tumor. The FDA approved targeted therapies vemurafenib and dabrafenib shrink or slow the growth of tumors in some people whose metastatic melanoma has a BRAF mutation. They can also help some patients live longerMelanoma Research Foundation https://www.melanoma.org/understand-melanoma/melanoma-treatment/targeted-therapy.
In patients with colorectal cancer, data suggest that a mutated BRAF gene, which is present in 5-10%Douillard JY, Oliner KS, Siena S, Tabernero J, Burkes R, Barugel M, et al. Panitumumab-FOLFOX4 treatment and RAS mutations in colorectal cancer. N Engl J Med. 2013 Sep 12. 369(11):1023-34. [Medline].Nelson R. Anti-EGFR therapy worsens survival in patients with RAS mutations. Medscape Medical News. September 11, 2013. Available at http://www.medscape.com/viewarticle/810817. Accessed: September 20, 2013.Berlin J. Beyond exon 2–the developing story of RAS mutations in colorectal cancer. N Engl J Med. 2013 Sep 12. 369(11):1059-60. [Medline]. http://emedicine.medscape.com/article/1690010-overview of tumors, can affect response to targeted agents. It is unclear to what extent the lack of response in KRAS wild-type colorectal cancer is due to BRAF mutations, but data suggest that mutated BRAF confers resistance to targeted therapy given beyond first-line treatment.
Non-Small Cell Lung
BRAF mutations occurs in a small proportion (1-4%)My Cancer Genome – BRAF in NSCLC https://www.mycancergenome.org/content/disease/lung-cancer/braf of patients with non-small cell lung cancer (NSCLC) that lack other driver mutations, such as KRAS and EGFR. The potential benefits of BRAF-inhibitors approved in the treatment of other tumor types are currently being investigated in multiple clinical studies.
In patients with Erdheim-Chester disease, approximately 50%Wikipedia – Erdheim-Chester Disease https://en.wikipedia.org/wiki/Erdheim%E2%80%93Chester_disease harbor mutations in the BRAF gene. Vemurafenib, an FDA approved targeted agent to the BRAF protein for melanoma, shows dramatic activity in patients whose tumor contains the BRAF mutation.
Traditional Testing for BRAF
Testing for the presence of a BRAF mutation has traditionally been performed on a tissue biopsy specimen obtained from the patient.
The FDA approved Cobas 4800 BRAF V600 Mutation Test is an in vitro diagnostic device intended for the qualitative detection of the BRAF V600E mutation in DNA extracted from formalin-fixed, paraffin-embedded human melanoma tissue. The Cobas 4800 BRAF V600 Mutation Test is a real-time PCR test on the Cobas 4800 system, and is intended to be used as an aid in selecting melanoma patients whose tumors carry the BRAF V600E mutation for treatment with vemurafenibU.S. Department of Health and Human Services http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/InVitroDiagnostics/ucm301431.htm.
BRAF gene mutation testing has emerged as an important tool for diagnosis, prognosis, treatment, and predicting patient outcome in response to targeted therapy. Evidence indicates BRAF gene mutation testing has a role in the followingMedscape – BRAF Gene Mutation Tests http://emedicine.medscape.com/article/2045309-overview#a4:
- Differentiating sporadic colorectal cancer with microsatellite instability-high (MSI-H) from hereditary nonpolyposis colorectal carcinoma (HNPCC) or Lynch syndrome
- Determining prognosis, as cancers with BRAF mutation are found to be more aggressive than their counterparts without the mutation, particularly in papillary thyroid carcinoma and colorectal carcinoma
- In treatment decisions, because in patients with advanced colorectal cancer, BRAF mutation testing has been suggested since its presence confers resistance to epidermal growth factor inhibitors (cetuximab and panitumumab), when k-ras is not mutated
- In therapeutic targeting, because the presence of mutated BRAF has been a valuable therapeutic target, particularly in metastatic melanoma
Studies continue to be published regarding the usefulness of detecting BRAF in various tumors in clinical practice. However, at present, BRAF mutation testing is only widely accepted for use in targeted therapy for advanced malignant melanoma. As more evidence emerges, BRAF mutation testing may become standard of care in the diagnosis and management of other cancers.
Liquid Biopsy Tests for BRAF Mutations
Certain fragments of DNA shed by tumors into the bloodstream can potentially be used to noninvasively detect BRAF mutations, monitor response to treatment and help explain why some cancers are resistant to therapies.
For most tumors, a tissue biopsy is challenging – it is costly, painful, or potentially risky for the patient. Circulating tumor DNA (ctDNA) urine and blood based liquid biopsy enables specific understanding of what kind of molecular changes are happening in the tumor in real time.
In order to address issues associated with tissue biopsy, the use of surrogate sources of DNA, such as blood or urine samples, which contain circulating tumor DNA (ctDNA), has emerged as a new strategy for tumor genotyping.
Today, circulating tumor DNA (ctDNA) may hold benefits that the traditional cancer diagnostic methods or tissue biopsies can’t offer such as detection through urine or blood without an invasive procedure like surgery. The evolution of sensitive ctDNA detection technologies has enabled the development of liquid biopsies with many clinical applications.
Trovagene Precision Cancer Monitoring
The use of Trovagene’s urine or blood liquid biopsy is only intended for detection and monitoring of mutations in patients previously diagnosed with cancer. It is not intended for screening of asymptomatic patients to diagnose cancer.
The Trovera Difference
Trovera liquid biopsy tests provide actionable information about mutations associated with common solid tumor cancers to aid physicians in choosing the right treatment for the right patient at the right time.
Noninvasive identification of clinically actionable mutations to inform treatment decisions.
Highly sensitive analysis of tumor dynamics.
Response to therapy, emergence of resistance mutation(s), disease progression and minimal residual disease.
References [ + ]
|1.||↑||Oncotarget. 2014 Dec; 5(23): 11752–11777.|
|2, 4.||↑||Solit DB, Rosen N. Resistance to BRAF inhibition in melanomas. N Engl J Med. 2011 Feb 24. 364(8):772-4. [Medline].|
|3, 5.||↑||Huang T, Zhuge J, Zhang WW. Sensitive detection of BRAF V600E mutation by Amplification Refractory Mutation System (ARMS)-PCR. Biomark Res. 2013 Jan 16. 1(1):3. [Medline].|
|6.||↑||Jemal A, Siegel R, Xu J, Ward E. Cancer statistics, 2010. CA Cancer J Clin. 2010 Sep-Oct. 60(5):277-300 [Medline].|
|7.||↑||Melanoma Research Foundation https://www.melanoma.org/understand-melanoma/melanoma-treatment/targeted-therapy|
|8.||↑||Douillard JY, Oliner KS, Siena S, Tabernero J, Burkes R, Barugel M, et al. Panitumumab-FOLFOX4 treatment and RAS mutations in colorectal cancer. N Engl J Med. 2013 Sep 12. 369(11):1023-34. [Medline].|
|9.||↑||Nelson R. Anti-EGFR therapy worsens survival in patients with RAS mutations. Medscape Medical News. September 11, 2013. Available at http://www.medscape.com/viewarticle/810817. Accessed: September 20, 2013.|
|10.||↑||Berlin J. Beyond exon 2–the developing story of RAS mutations in colorectal cancer. N Engl J Med. 2013 Sep 12. 369(11):1059-60. [Medline]. http://emedicine.medscape.com/article/1690010-overview|
|11.||↑||My Cancer Genome – BRAF in NSCLC https://www.mycancergenome.org/content/disease/lung-cancer/braf|
|12.||↑||Wikipedia – Erdheim-Chester Disease https://en.wikipedia.org/wiki/Erdheim%E2%80%93Chester_disease|
|13.||↑||U.S. Department of Health and Human Services http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/InVitroDiagnostics/ucm301431.htm|
|14.||↑||Medscape – BRAF Gene Mutation Tests http://emedicine.medscape.com/article/2045309-overview#a4|