Characterization and Clinical Utility of BRAFV600 Mutation Detection Using Cell-Free DNA in Patients with Advanced Melanoma

Simple Summary

The choice of cancer drug(s) for the treatment of advanced melanoma is based on the types of gene alterations that are present in the patient’s tumor(s). Sometimes, the tumor sample that is obtained from surgery may be degraded, and the test does not provide a reliable result, leading to the selection of the wrong treatment, and, consequently, poor outcomes for the patient. Surgery to obtain fresh tumor samples is inconvenient. In recent years, scientists have learned that fragments of genes from dying cells, including tumors, are constantly being released into the blood. This study shows that the presence of altered genes can be reliably determined using easy-to-obtain blood samples. The study also shows that, while there is a small rate of error with the commonly used tests based on the tumor tissue sample, retests using blood samples may be a less invasive and rapid alternative for identifying the BRAF mutation status and selecting the right treatment for these patients.

Abstract

Tissue-based tests for BRAF^V600 mutation-positive melanoma involve invasive biopsy procedures, and can lead to an erroneous diagnosis when the tumor samples degrade. Herein, we explored a minimally invasive, cell-free deoxyribonucleic acid (cfDNA)-based platform, to retest patients for BRAF^V600 mutations. This phase 2 study enrolled adult patients with unresectable/metastatic melanoma. A prescreening testing phase evaluated the concordance between a prior tissue-based BRAF^V600 mutation test result and a subsequent plasma cfDNA-based test result. A treatment phase evaluated the patients who were confirmed as BRAF^V600 mutation-positive, and were treated with cobimetinib plus vemurafenib. It was found that 35/54 patients (64.8%) with a mutant BRAF status by prior tissue test had a positive BRAF^V600 mutation with the cfDNA test. Further, 7/118 patients (5.9%) with a wild-type BRAF status had a positive BRAF^V600 mutation cfDNA test; tissue retests on archival samples confirmed BRAF^V600 mutation positivity in 5/7 patients (71.4%). One of these patients received BRAF pathway-targeted therapy (cobimetinib plus vemurafenib), and had progression-free survival commensurate with previous experience. In the overall cobimetinib plus vemurafenib-treated population, 29/36 patients (80.6%) had an objective response. The median progression-free survival was 13.6 months (95% confidence interval, 9.5–16.5). Cell-free DNA–based tests may be a fast and convenient option to identify BRAF mutation status in melanoma patients, and help inform treatment decisions.

Management of melanoma brain metastases

Relapses in the brain remain a major obstacle to cure in many patients with advanced melanoma. At present, the management of melanoma brain metastases continues to rely heavily on surgical and radiotherapeutic interventions, which have become safer and more effective with modern imaging, surgery and radiation technologies. Additionally, novel targeted and immunotherapeutic agents, shown to generate meaningful intracranial response and survival benefit in patients with melanoma brain metastases when compared with historical controls, expand systemic treatment options for this subset of patients. These systemic therapies become particularly important when intracranial disease burden precludes neuro- or radio-surgery. Considerable multidisciplinary research effort is ongoing to improve outcomes for melanoma patients with brain metastases, a key challenge in the management of advanced melanoma.

Dabrafenib therapy for advanced melanoma

OBJECTIVE

To summarize the clinical development of dabrafenib and to highlight the clinically relevant distinct characteristics of dabrafenib in contrast to vemurafenib.

DATA SOURCE

An English-language literature search of MEDLINE/PubMed (1966-June 2013), using the keywords GSK2118436, dabrafenib, vemurafenib, selective BRAF inhibitor, and advanced melanoma, was conducted. Data were also obtained from package inserts, meeting abstracts, and clinical registries.

STUDY SELECTION AND DATA EXTRACTION

All relevant published articles on dabrafenib and vemurafenib were reviewed. Clinical trial registries and meeting abstracts were used for information about ongoing studies.

DATA SYNTHESIS

BRAF(V600E) mutation confers constitutive BRAK kinase activation in melanoma cells, promoting tumor growth. This discovery led to the development of BRAF kinase inhibitors like vemurafenib and dabrafenib. Dabrafenib has been approved to treat patients with BRAF(V600E)-positive unresectable or metastatic melanoma based on its clinical benefit demonstrated in a randomized phase III study. It has also been shown to be safe and effective in patients with BRAF mutant advanced melanoma involving the brain. Dabrafenib is well tolerated, with the most common adverse effects being hyperkeratosis, headache, pyrexia, and arthralgia. Currently, there is no evidence to suggest that one BRAF inhibitor is superior to the other. With similar efficacy, therapy selection will likely be influenced by differential tolerability and cost.

CONCLUSIONS

Dabrafenib joins vemurafenib to confirm the superior clinical outcome of the BRAF inhibitors when compared with dacarbazine in patients with BRAF(V600E)-positive advanced melanoma. Active research is ongoing to expand its utility into the adjuvant setting and to circumvent rapid emergence of drug resistance.

Cutaneous effects of BRAF inhibitor therapy: a case series

BACKGROUND

The cutaneous effects of rapidly accelerated fibrosarcoma kinase B (BRAF) inhibitors are not well understood. Squamous cell carcinoma (SCC), keratoacanthoma, and photosensitivity have been described in patients taking BRAF inhibitors.

PATIENTS AND METHODS

To characterize the timing and frequency of skin lesions in patients receiving BRAF inhibitor therapy, we utilized a retrospective case review of 53 patients undergoing treatment with BRAF inhibitors for 4-92 weeks of therapy. Patients were evaluated at baseline, and then followed at 4- to 12-week intervals. Charts were retrospectively reviewed, and the morphology and timing of cutaneous events were recorded.

RESULTS

Thirty-three of the 53 charts met exclusion/inclusion criteria, 15 were treated with vemurafenib, and 18 were treated with GSK 2118436/GSK 1120212. Of 33 patients treated with BRAF inhibitor, 13 developed photosensitivity (39.4%), 10 developed actinic keratoses (30.3%), 10 developed warts (30.3%), and 6 developed SCC (18.2%).

CONCLUSIONS

Multiple cutaneous findings were observed in the 33 patients taking BRAF inhibitors. The previously described association with SCC and photosensitivity was observed in these patients as well. Over half of the observed SCCs were invasive in nature. Photosensitivity continues to be frequent with BRAF inhibitors. Patients taking BRAF inhibitors should have regular full body skin exams. Further studies are necessary to better elucidate the rates of these adverse cutaneous effects.