About half of all melanomas contain somatic mutations that result in constitutive activation of the BRAF kinase, leading to hyperactive signaling of the growth-promoting mitogen- activated protein kinase (MAPK) pathway.

Systemic therapies with selective smallmolecule inhibitors of the BRAF kinase, both in monotherapy and in combination with inhibitors of the MEK kinase, can extend survival and reduce recurrence risk in patients with 

 mutation testing has therefore become an essential tool in the diagnostic workup and management of patients with advanced melanoma.

According to Keith T. Flaherty, MD, director of Developmental Therapeutics at the Massachusetts General Hospital Cancer Center in Boston, “At the moment, the only molecular feature in melanoma that is critical to treatment decision making is the presence or absence of a 

 are present in 40% to 60% of all melanoma cases, with more than 90% of mutations found at codon 600 in exon 15.

The activating V600E amino acid substitution is by far the most common V600 mutation and accounts for 74% to 95% of these mutations, followed by V600K in 5% to 30%, V600R in 5% to 7%, and V600M in about 4%.

 More rare mutations include V600D and mutations in other codons with activating, impairing, or unknown effects on kinase activity.

Clinical evidence for the activity of selective BRAF inhibitors derives from trials that were largely restricted to patients with 

-mutant tumors, as concurrently developed 

 mutation testing assays were optimized for the detection of these 2 most common mutations.

Prospective testing of the BRAF inhibitors vemurafenib (Zelboraf) and dabrafenib (Tafinlar) as single agents in phase III trials was conducted among patients with 

-positive metastatic melanoma, demonstrating response rates in the range of 50%, clinical benefit rates close to 90%, and prolongation of progression-free survival (PFS) and overall survival (OS) compared with dacarbazine.

Similarly, phase III studies with combination regimens of dabrafenib plus trametinib (Mekinist) or vemurafenib with cobimetinib (Cotellic) revealed significant PFS and OS benefits with dual BRAF/MEK inhibition over single agent BRAF inhibitors. Patients with 

mutant melanoma represented the majority of the study population.

Indications for these agents based on phase III trial data therefore incorporate the presence of specific mutations. Combination dabrafenib/ trametinib and vemurafenib/cobimetinib therapies and single-agent trametinib are indicated for the treatment of patients with 

 mutations, whereas approved use of single-agent vemurafenib or dabrafenib is limited to the treatment of patients with 

This rationale is supported by findings that 

 mutation type can affect response to treatment with selective BRAF inhibitors. Phase II study findings have shown that, although dabrafenib is active in patients with 

-mutant tumors, ORR and PFS in this subgroup were lower than in patients with 

 However, evidence also exists that patients with less common 

 mutations not represented in phase III trials can benefit from BRAF inhibitor therapy.

In a cohort study including patients with 

 mutations (n = 9), objective responses to monotherapy with selective BRAF inhibitors (dabrafenib or vemurafenib) were seen in 5 of 6 patients evaluable for response assessment. The 

 mutation is common in males and those with ulcerated primary melanomas. Similar to 

 is more frequently observed in older individuals.

According to study author Oliver Klein, MD, of Austin Health in Heidelberg, Australia, and colleagues, these partial responses occurred rapidly and included “a reduction in the size of lung metastases, liver metastases, stabilization of brain metastases, and a marked reduction in subcutaneous metastases to the scalp. The rapid clinical responses of patients with 

 mutation-positive melanoma mirror those observed in patients with 

 mutations, indicating that selective BRAF inhibitors are active against melanoma with this genotype.”

Other reports have shown responses to selective BRAF inhibitors in patients with V600R alterations, including a case report of a patient who responded to vemurafenib treatment

and a phase II study of patients with discrepant genotyping results for 

, who had a confirmed partial response to trametinib with a PFS of at least 57 weeks.

 mutation status in patients with melanoma is essential for the selection of first-line therapy. Adequate genetic testing relies on a sequence of processes that includes selection of tissue source, biopsy approach, specimen preparation and evaluation of tumor content, and choice of test assay.

According to current recommendations, routine BRAF testing of the primary cutaneous melanoma should not be performed in patients without metastatic disease. In patients with metastatic disease, biopsy of the metastatic lesion, if feasible, is considered the preferred method to obtain sufficient tissue for genetic testing, if systemic therapy is planned, but archival material can also be used.

According to Flaherty, these recommendations are based on observations that 

 mutations arise early during melanocytic proliferation and that up to 80% of benign nevi also harbor 

 mutations, rendering mutation testing of primary tumor tissue non-informative.

“The best available evidence indicates that BRAF mutations are stably present in all tumor cells in lymph node and visceral metastases, whereas there can be heterogeneity in the primary melanoma. [This supports] the recommended practice of performing 

 mutation testing in metastatic tumor sites, with previously resected regional lymph nodes [for patients who had stage III disease prior to developing stage IV disease] being a reliable source of tumor material for this testing,” Flaherty said.

Tumor molecular profiling is usually conducted on DNA extracted from formalin-fixed paraffin-embedded (FFPE) tissue specimens after pathological examination has confirmed the presence of tumor cells and determined tumor content. Factors that may affect testing results include tissue integrity, presence of high levels of pigmentation, or lymphocyte infiltration.

According to Monika Jurkowska, PhD, with Genomed Health Center in Warsaw, Poland, and colleagues, key steps for reliable testing involve the selection of “block surface with sufficient tumor cellularity (>5%-20% depending of the analytical sensitivity of the applied method and feasibility of subsequent dissection) but also without extensive necrosis, blood or melanin pigments content.”

Validated approaches for the detection of 

 mutations in FFPE tumor material tissue include polymerase chain reaction (PCR)-based assays, sequencing technologies (Sanger, pyrosequencing, next generation sequencing [NGS]) or immunohistochemistry, among others.

Methods differ in sensitivity, specificity, and cost. Depending on scope, detection methods can be broadly grouped into targeted assays that only identify a genetic alteration of interest such as allele-specific PCR tests, and screening assays that can simultaneously identify all mutations in a larger genomic region such as bidirectional direct Sanger sequencing.

Direct sequencing is highly specific but has a relatively low sensitivity (80%-93.4%), requiring a relatively high proportion of mutant tumor cells within the sample.

 High resolution melt (HRM) analysis and Sanger sequencing technologies have proved highly specific and relatively sensitive (100% specific and up to a 6.6% allele frequency sensitivity), whereas pyrosequencing is sensitive (5% allele frequency) but less specific (90%).

PCR-based tests have a higher sensitivity than Sanger sequencing (97.5%) and require only small amounts of DNA. The FDA-approved cobas 4800 

 and THxID-BRAF tests were developed concurrently with vemurafenib and dabrafenib, respectively, and were optimized to detect the 2 most common 

, with differences in specificity. The cobas 4800 

 mutation test received approval along with vemurafenib as a companion diagnostic.

 This targeted assay combines allele-specific real-time PCR and TaqMelt technology to determine 

 mutation status in DNA isolated from FFPE tumor tissue and has an approximate sensitivity of 5% mutation- bearing cells in a mixed sample.

 mutation (98%) but also has cross-reactivity with V600K (approximately 50%), and with 

 The test only identifies the presence of a mutation without differentiation between mutations and does not reliably detect 

The THxID-BRAF test was developed to identify melanoma patients with 

 mutations for treatment with dabrafenib and trametinib. 

 This PCR-based assay incorporates an internal control to validate adequate DNA integrity and relies on primers that are specific for each of the 2 mutations. The assay is largely non-cross reactive with other 

 mutations with high concordance with HRM analysis and Sanger sequencing results (95.9%).

Based on studies comparing PCR-based assays with sequencing approaches, the exclusive use of PCR-based assays for the detection of 

 mutations will fail to identify patients with more rare mutations, such as 

, who may also benefit from targeted therapy.

Comparison of PCR/Sanger sequencing assays with the cobas 4800 

 test in archival material (236 FFPE samples, cutaneous melanoma with lymph node metastases) found that both methods detected 

 mutations at a similar rate (60.9% vs 61.0%), with a concordance of 95.2%.

 Sanger sequencing failed to produce results in 2.5% of samples but was highly specific and reproducible in identifying 

 mutations, whereas the cobas assay produced results for all samples but false-negative results in 2.5% of samples that contained 

 mutation detection methods in 295 melanoma FFPE samples found that, relative to Sanger sequencing, the cobas 4800 

 test had only 80.5% sensitivity (95% CI, 72.4%-86.6%; 118 vs 96 of 275 samples).

 False-negative samples per cobas assay included tumors in which sequencing identified 

Kevin Qu, with Quest Diagnostics Nichols Institute, and coauthors explained that the presence of more than 1 mutant nucleotide (dinucleotide) could affect test outcomes: “The cobas test is a single-oligonucleotide probe-based test that has greater analytical sensitivity than Sanger sequencing. However, as our findings suggest, its specificity for a single-nucleotide mutation means that it may miss relevant dinucleotide mutations in some cases. Sanger sequencing can detect single-nucleotide and dinucleotide mutations in the same region, which accounts for its higher detection rate in this study.”

To address this, an ideal testing strategy may call for samples that test negative according to PCR assays to be additionally validated by a second sequencing approach that reliably identifies non-

 mutations, or confirm their absence. This may represent a practical and comprehensive strategy to identify patients with 

Qu and coauthors conclude, “use of Sanger sequencing as a second-line test for samples that are negative on the cobas assay could be a rational approach to maximizing the potential benefit of vemurafenib.”

Similarly, Jurkowska and coauthors argued that, “by definition, cobas cannot detect activating 

 mutation located outside codon V600. For those variants, detection based on sequence analysis (Sanger/ NGS seems to be [the] method of choice at the current state.”

According to the authors, once sufficient knowledge about the significance of other 

 mutations for melanoma treatment decisions has accumulated, efforts will also need to focus on the “optimal mode of detection, since targeted genotyping would not cover all possibilities.”

NCCN. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) Melanoma. NCCNorg. 2016;Version 2.2016.

Klein O, Clements A, Menzies AM, et al. BRAF inhibitor activity in V600R metastatic melanoma. 

Lovly CM, Dahlman KB, Fohn LE, et al. Routine multiplex mutational profiling of melanomas enables enrollment in genotype-driven therapeutic trials. 

Zheng G, Tseng LH, Chen G, et al. Clinical detection and categorization of uncommon and concomitant mutations involving BRAF. 

Chapman PB, Hauschild A, Robert C, et al. Improved survival with vemurafenib in melanoma with BRAF V600E mutation. 

Hauschild A, Grob JJ, Demidov LV, et al. Dabrafenib in BRAF-mutated metastatic melanoma: a multicentre, open-label, phase 3 randomised controlled trial. 

Long GV, Stroyakovskiy D, Gogas H, et al. Dabrafenib and trametinib versus dabrafenib and placebo for Val600 BRAF-mutant melanoma: a multicentre, double-blind, phase 3 randomised controlled trial. 

Robert C, Karaszewska B, Schachter J, et al. Improved overall survival in melanoma with combined dabrafenib and trametinib. 

Larkin J, Ascierto PA, Dreno B, et al. Combined vemurafenib and cobimetinib in BRAF-mutated melanoma.

Long GV, Trefzer U, Davies MA, et al. Dabrafenib in patients with Val600Glu or Val600Lys BRAF-mutant melanoma metastatic to the brain (BREAK-MB): a multicentre, open-label, phase 2 trial. 

Ascierto PA, Minor D, Ribas, A et al. Phase II trial (BREAK-2) of the BRAF inhibitor dabrafenib (GSK2118436) in patients with metastatic melanoma. 

van den Brom RR, de Vries EG, Schroder CP, Hospers GA. Effect of vemurafenib on a V600R melanoma brain metastasis. 

Kim KB, Kefford R, Pavlick AC, et al. Phase II study of the MEK1/MEK2 inhibitor Trametinib in patients with metastatic BRAF-mutant cutaneous melanoma previously treated with or without a BRAF inhibitor.

US Food & Drug Administration. Summary of safety and effectiveness data. THxIDTM BRAF Kit for use on the ABI 7500 Fast Dx Real-Time PCR Instrument. http://goo.gl/ZVdBiS. Approved May 29, 2013. Accessed August 18, 2016.

US Food & Drug Administration. List of cleared or approved companion diagnostic devices (in vitro and imaging tools). http://goo.gl/YqNesG. Updated June 9, 2016. Accessed August 16.

Jurkowska M, Gos A, Ptaszynski K, et al. Comparison between two widely used laboratory methods in BRAF V600 mutation detection in a large cohort of clinical samples of cutaneous melanoma metastases to the lymph nodes.

US Food & Drug Administration. Summary of safety and effectiveness data. Cobas 4800 BRAF V600 Mutation Test. Approved August 17, 2011. Accessed August 18, 2016.

Spagnolo F, Ghiorzo P, Orgiano L, et al. BRAF-mutant melanoma: treatment approaches, resistance mechanisms, and diagnostic strategies. 

Ihle MA, Fassunke J, Konig K, et al. Comparison of high resolution melting analysis, pyrosequencing, next generation sequencing and immunohistochemistry to conventional Sanger sequencing for the detection of p.V600E and non-p.V600E BRAF mutations. 

Halait H, Demartin K, Shah S, et al. Analytical performance of a real-time PCR-based assay for V600 mutations in the BRAF gene, used as the companion diagnostic test for the novel BRAF inhibitor vemurafenib in metastatic melanoma. 

Marchant J, Mange A, Larrieux M, Costes V, Solassol J. Comparative evaluation of the new FDA approved THxID-BRAF test with High Resolution Melting and Sanger sequencing. 

Heinzerling L, Kuhnapfel S, Meckbach D, et al. Rare BRAF mutations in melanoma patients: implications for molecular testing in clinical practice.

Qu K, Pan Q, Zhang X, et al. Detection of BRAF V600 mutations in metastatic melanoma: comparison of the Cobas 4800 and Sanger sequencing assays.

Articles

BRAF mutation testing has become an essential tool in the diagnostic workup and management of patients with advanced melanoma. Activating mutations of BRAF are present in 40% to 60% of all melanoma cases, with more than 90% of mutations found at codon 600 in exon 15.

A Closer Look at BRAF Melanoma Testing Reveals Intricacies of V600 Mutation

A long-term analysis has shown that approximately one-fifth of patients with 

V600-mutant melanoma who were treated with the combination of dabrafenib (Tafinlar) and trametinib (Mekinist) remained progression-free after 3 years, suggesting a plateau of the survival curve.

According to lead author Georgina Long, MD, with the Melanoma Institute Sydney, Australia, and co-authors,

 this defines, “a need to understand the characteristics of patients who derive the greatest benefit from each mode of therapy.” Specifically, “future selection of patients for combined BRAF and MEK inhibition, and the rational design of clinical trials for those who fail it, may be assisted by an analysis of the clinicopathological features of those experiencing long-term benefit and those who progress.”

In their study, Long and colleagues found that good prognostic features such as normal lactate dehydrogenase (LDH) levels, earlier-stage melanoma, and fewer metastatic sites were consistently associated with durable response and prolonged overall survival (OS) with BRAF/MEK inhibitor therapy.

 Patients who survived longest on treatment included those with a complete response (CR), according to RECIST, and patients with a normal baseline LDH (63% and 62%, respectively). Data were from 2 cohorts of BRAF-inhibitor naïve patients (n = 78) who had been treated with dabrafenib (150 mg twice daily) plus trametinib (2 mg daily).

Similarly, a study evaluating long-term outcomes of patients who received either BRAF or combined BRAF and MEK inhibitor regimens in phase I to III trials with single agent dabrafenib or vemurafenib, or combined dabrafenib/trametinib found that female sex and normal pretreatment LDH levels were the only factors associated with longer progression-free survival (PFS) and OS.

As the development of novel targeted and immunotherapeutic agents have demonstrated more efficacy versus traditional chemotherapy, treatment paradigms in melanoma have significantly evolved. Current recommendations for first-line systemic therapy for patients with advanced or metastatic melanoma consider 

mutation status, tumor growth rate, and the presence or absence of cancer-related symptoms. 

Immunotherapies with agents that block CTLA-4 or PD-1/PD-L1 checkpoints have been associated with durable responses in a subset of patients, and are often considered for patients with low-volume, asymptomatic metastatic melanoma. Targeted therapies, on the other side, are preferred for patients with 

-mutant tumors who have symptomatic disease and benefit from the rapid response associated with these agents.

A main concern with targeted therapies is tumor resistance that ultimately develops in most patients within 6-12 months. However, as Jason J. Luke, MD, with the University of Chicago Medicine states, “A sizable fraction of patients do very, very well for a long time on targeted therapy.”

In the study by Long and colleagues, LDH below the upper limit of normal (ULN) was significantly associated with prolonged survival of patients receiving BRAF/MEK inhibitor combination therapy with dabrafenib/trametinib.2 Patients with a normal LDH at baseline had a median OS of 45.5 months (95% CI, 45.5 to not reached) compared with 16.6 months (95% CI, 11.1-22.6) for patients with an elevated LDH.

 Overall survival rates of patients with normal versus elevated LDH levels at baseline, respectively, were 88% versus 68% at 1 year, 75% versus 18% at 2 years, and 62% versus 5% at 3 years.

Recent data from phase III COMBI-v trial have also linked baseline LDH serum levels to survival benefits with the dabrafenib/trametinib combination.

 According to lead author Caroline Robert, MD, of Institut Gustave Roussy in Paris, “The longest benefit was in patients with an LDH less than or equal to the upper limit of normal, who had a 2-year overall survival rate of 66% and a median progression-free survival of 17.5 months.” 

In this patient group, median OS was not yet reached with dabrafenib/trametinib and was 21.5 months with vemurafenib (HR, 0.56), translating to a 44% OS benefit with the combination. Patients with an LDH above the ULN had less benefit with a median OS of 10.6 months with the combination and 8.9 months with vemurafenib monotherapy (HR, 0.81).

Similar observations are emerging from the phase III evaluation of cobimetinib/vemurafenib. OS benefits of the combination were observed in all patient subgroups.

 For patients with both LDH baseline levels, median OS was not reached with the combination and was 23.3 months with vemurafenib. Patients with elevated LDH levels had an OS of 14.8 months with the combination and 11.2 months with vemurafenib alone. According to lead author Victoria Atkinson, MD, of the Princess Alexandra Hospital in Queensland, Australia, “This is consistent with previous combination studies showing that patients with poor prognostic factors do worse.”

Longer-term analyses of patients who had received both BRAF monotherapy and combined BRAF/MEK therapy have also reported a significant association of normal LDH levels with prolonged survival. Patients with normal LDH levels had a median OS of 23.5 months compared with 7.3 months in patients with elevated LDH levels.

Across all studies, normal serum LDH levels correlated with continued long-term response without progression (per Cox proportional hazards regression analysis; 

 = .024,2 or per univariate and multivariate analyses).

 In COMBI-v, in patients with low LDH levels, median PFS was 17.5 and 9.2 months with the combination and monotherapy, respectively (HR, 0.55) and 5.5 versus 4.0 months in patients with elevated LDH levels (HR, 0.70).

According to Alexander Menzies, MBBS, with the Melanoma Institute Sydney, Australia, and co-authors,

 this evidence “suggests that LDH is not simply prognostic. The biology of metastatic tumors that produce different levels of LDH may be distinct; for example, it has been shown that a high serum LDH level reflects an anaerobic oxidative metabolic state. As such, the best treatments for metastatic patients with normal and elevated LDH levels may be different.”

 According to Robert, patients with “low LDH respond extremely well to targeted treatment. Patients with high LDH, whatever treatment we use, remain a big medical need. They derive a small benefit each time we evaluate a new, effective therapy. The benefit is always less in this population.” 

Tumor Burden and Timing of BRAF MEK Inhibitor Therapy

Consistent features associated with better outcomes with combined BRAF/MEK inhibitor in long-term analyses also included earlier-stage melanoma and fewer metastatic sites. Furthermore, according to Long and co-authors, “good prognostic features at progression seemed to prolong survival from the time of progression but were also associated with receiving subsequent systemic therapy.”

TABLE 1. Survival by Baseline Characteristics With Dabrafenib/Trametinib

Abbreviations: LDH, lactate dehydrogenase; ULN, upper limit of normal.

TABLE 2. Survival Comparison by Baseline Characteristics With Dabrafenib/Trametinib

The presence of less than 3 organ disease sites was a baseline feature that met stringent criteria for association with longer OS (Cox proportional hazard regression analysis).

 The median OS in patients with less than 3 metastatic sites was 45.5 versus 17.5 months in patients with ≥3 metastatic sites (HR, 0.36; 95% CI, 0.18-0.69).

 The corresponding OS rates were 92% versus 68% at 1 year, 73% versus 30% at 2 years, and 58% versus 19% at 3 years.

 In patients with earlier stage disease (IIIC/M1a/M1b vs M1c), the median OS had not been reached and was 21.9 months in patients with M1c stage disease (HR, 0.36; 95% CI, 0.18-0.72). Other baseline features evaluated, including age, sex, ECOG performance status, and prior immunotherapy, did not correlate with added benefit from combination therapy 

Several indicators of a good prognosis, including the presence of fewer than three metastatic organ sites, lower median sum of diameters, lower melanoma stage, lower ECOG performance status, and no history of brain metastases were baseline factors that were also more frequent among patients who had a continued long-term response without progression.

 Consistent with these observations, patients who progressed and did not receive further systemic chemotherapy had higher ECOG performance status, higher LDH, larger sum of diameters of RECIST target lesions at progression, greater absolute change in the RECIST sum of diameters from nadir, progression in the brain, and female sex 

Findings that low tumor burden predicts superior long-term outcomes imply that BRAF/MEK inhibitor therapy should also be considered earlier in the disease course, in healthier patients with lower disease burden, in whom immunotherapy is often preferred. Long and co-authors noted that, “on the basis of longer-term survival data from the current study and other studies, it would not be possible to use baseline features to select one therapy over another. Specifically, this study showed that long-term survival and durable responses with dabrafenib plus trametinib are associated with good prognostic features at baseline, including factors associated with low-volume disease—classically considered a hallmark for frontline immunotherapy.” 

Observations from a phase Ib trial have also identified tumor burden as a predictor of clinical outcome with BRAF/MEK inhibition with vemurafenib and cobimetinib.

 This study involved 35 BRAF inhibitor-naïve patients with 

V600-mutant melanoma and found that early and progressive metabolic response of tumors to dual inhibitor therapy was associated with improved OS. Lead author Grant A. McArthur, MBBS, PhD, with the Peter MacCallum Cancer Centre, Melbourne, Australia, and colleagues evaluated several 18-F-fluorodeoxyglucose (FDG) uptake measures on positron emission tomography (PET) as indicators of tumor burden and glycolytic metabolism in tumors.

Patients with low values of tumor burden measures at baseline compared with the median (percentage injected dose <0.36% or metabolic tumor volume < 47.5 ml) had a longer OS than patients with tumor burden measures above the median (HR, 0.19, 

The ORR to treatment was 87% by RECIST and median PFS was 13.7 months. Complete metabolic responses (CMR) were obtained by 51% of patients during the second treatment cycle, and patients achieving CMR during the first treatment cycle (14%) had a longer PFS than patients achieving a partial MR (>30% decrease in standard maximum uptake volume; 86%). Tumor burden at baseline was not correlated with metabolic response.

On-Treatment Features and Biomarkers of Response

The authors concluded that, “Marked, early and progressive metabolic response on FDG-PET [was] consistent with successful inhibition of ERK-signaling.”

 According to lead author McArthur, these findings fit in with hypotheses that suggest that, “Enhanced inhibition of the RAF/MEK/ERK pathway may lead to more cell death or even a change in tumor microenvironment that is less compatible with long-term cell survival or the reacquisition of a proliferative state […] and that more effective or complete inhibition of RAF/MEK/ERK signaling may indeed produce biological responses that improve overall survival.”

Both degree of response and response category have been linked with benefit for targeted therapies. Patients with a complete response (CR; per RECIST) to the combination of dabrafenib/trametinib had numerically higher OS rates than patients with partial response (PR) or stable disease (SD). OS rates at 1, 2, and 3 years were 100%, 88%, and 63% for patients with CR versus 79%, 48%, and 33% for patients with PR, and 69%, 35%, and 35% for patients with SD.

Among patients receiving either BRAF inhibitor monotherapy or BRAF/MEK inhibitor combination regimens, the RECIST response correlated with PFS and OS (both 

<.001) as a continuous variable, and patients with CR had longer PFS and OS.

 According to the authors of this study, the association of potential biomarkers that may associate with response and clinical outcome is complex, because “Mixed responses to treatment often occur with BRAF inhibitors, in which some metastases shrink while others remain stable or grow. Such responses are probably a consequence of molecular heterogeneity, which further affects clinical outcome and confounds biomarker studies.” 

Candidate biomarkers of response identified in small studies include markers of MAPK pathway activation and TORC1 activity early during treatment, PTEN status, cell cycle gene aberrations (CCND1 and CDKN2A copy number), and stromal growth factor expression.

Recent findings from the phase III coBRIM trial of vemurafenib/cobimetinib versus vemurafenib indicate that the presence of co-existing oncogenic mutations in addition to 

V600 does not impact response to combination treatment.

, or receptor tyrosine kinases (RAS/RAF/RTK) were detected in 11% (n = 46) of the study population, and resulted in higher levels of ERK and MEK activation in tumors as detected by protein analysis. However, no correlation with PFS or ORR was identified.

The analysis of biomarkers that may correlate with response to treatment and treatment toxicity is the focus of an ongoing randomized phase III study (ClinicalTrials.gov identifier NCT02314143). The 3-arm study has been designed to assess sequential effects of BRAF and MEK inhibition on skin, blood and tumor biomarkers, and will compare continuous dabrafenib/trametinib combination therapy with upfront monotherapy with dabrafenib or trametinib followed by combination therapy. 

Long GV, Weber JS, Infante JR, et al. Overall Survival and Durable Responses in Patients With BRAF V600-Mutant Metastatic Melanoma Receiving Dabrafenib Combined With Trametinib. 

National Comprehensive Cancer Network (NCCN). NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®): Melanoma. 

Menzies AM, Wilmott JS, Drummond M, et al. Clinicopathologic features associated with efficacy and long-term survival in metastatic melanoma patients treated with BRAF or combined BRAF and MEK inhibitors. 

Robert C, Karaszewska B, Schachter J, et al. Two year estimate of overall survival in COMBI-v, a randomized, open-label, phase III study comparing the combination of dabrafenib (D) and trametinib (T) with vemurafenib (Vem) as first-line therapy in patients (pts) with unresectable or metastatic BRAF V600E/K mutation-positive cutaneous melanoma. Presented at: 2015 European Cancer Congress; September 25-29; Vienna, Austria Abstract 3301. 

Atkinson V, Larkin J, McArthur GA, et al. Improved overall survival with cobimetinib (COBI) and vemurafenib (VEM) in advanced BRAFV600-mutated melanoma and biomarker correlates of efficacy. Presented at: 12th International Congress of the Society for Melanoma Research in San Francisco, California, 21 November 2015. 

McArthur GA, Callahan J, Ribas A, et al. Metabolic tumor burden for prediction of overall survival following combined BRAF/MEK inhibition in patients with advanced BRAF mutant melanoma. 

McArthur GA. Combination Therapies to Inhibit the RAF/MEK/ERK Pathway in Melanoma: We are not Done Yet. 

Larkin J, Yan Y, McArthur GA, et al. Update of progression-free survival (PFS) and correlative biomarker analysis from coBRIM: Phase III study of cobimetinib (cobi) plus vemurafenib (vem) in advanced BRAF-mutated melanoma. 

A long-term analysis has shown that approximately one-fifth of patients with BRAF V600-mutant melanoma who were treated with the combination of dabrafenib (Tafinlar) and trametinib (Mekinist) remained progression-free after 3 years, suggesting a plateau of the survival curve.

Sigrid Eckardt

Articles

A Closer Look at BRAF Melanoma Testing Reveals Intricacies of V600 Mutation

Prognostic Factors Link to Longer OS With MEK/BRAF Combo in Melanoma