Comparison of targeted next generation sequencing (NGS) versus isolated BRAF V600E analysis in patients with metastatic melanoma

BRAF testing modalities in histiocytic disorders: Comparative analysis and proposed testing algorithm

OBJECTIVES

Understanding of histiocytic disorders has been revolutionized by demonstration of mitogen-activated protein kinase (MAPK) pathway mutations, most commonly BRAFV600E. The optimal testing strategy to assess BRAFV600E is unknown. We aimed to compare performance of testing modalities, to propose a framework for evaluation of BRAFV600E mutation status in histiocytic disorders.

METHODS

We retrospectively reviewed patients with histiocytic disorders and BRAF mutation testing on a lesional tissue specimen.

RESULTS

In 120 patients, BRAF assessment included immunohistochemistry (IHC) in 97 (80.2%), polymerase chain reaction (PCR) in 35 (28.9%), and next-generation sequencing (NGS) in 62 (51.2%). Forty-five underwent both NGS and IHC. With NGS as the gold standard, the sensitivity and specificity of IHC were 82.4% and 96.4%. Three false negatives were observed in biopsy specimens with low BRAFV600E variant allele frequency or decalcified tissue. One false-positive IHC was observed in a lung biopsy specimen, likely due to antibody cross-reactivity with respiratory cilia. Among 14 with successful NGS and PCR, a single discordance was observed. Two PCR-to-IHC discrepancies were observed, including one other false-positive IHC.

CONCLUSIONS

Immunohistochemistry was highly specific for detection of BRAFV600E. Main caveats were false negatives and lack of detection of non-BRAFV600E mutations. We propose the use of IHC as initial screening in general practice with reflex molecular testing if negative.

BRAFV600E Mutant Allele Frequency (MAF) Influences Melanoma Clinicopathologic Characteristics

BACKGROUND

Cutaneous melanoma shows high variability regarding clinicopathological presentation, evolution and prognosis.

METHODS

Next generation sequencing was performed to analyze hotspot mutations in different areas of primary melanomas (MMp) and their paired metastases. Clinicopathological features were evaluated depending on the degree of variation of the BRAFV600E mutant allele frequency (MAF) in MMp.

RESULTS

In our cohort of 14 superficial spreading, 10 nodular melanomas and 52 metastases, 17/24 (71%) melanomas had a BRAFV600E mutation and 5/24 (21%) had a NRASQ61 mutation. We observed a high variation of BRAFV600E MAF (H-BRAFV600E) in 7/17 (41%) MMp. The H-BRAFV600E MMp were all located on the trunk, had lower Breslow and mitotic indexes and predominantly, a first nodal metastasis. Regions with spindled tumor cells (Spin) and high lymphocytic infiltrate (HInf) were more frequent in the H-BRAFV600E patients (4/7; 57%), whereas regions with epithelial tumor cells (Epit) and low lymphocytic infiltrate (LInf) were predominant (6/10; 60%) and exclusive in the low BRAFV600E MAF variation tumors (L-BRAFV600E). The H-BRAFV600E/Spin/HInf MMp patients had better prognostic features and nodal first metastasis.

CONCLUSIONS

The H-BRAFV600E MMp were located on the trunk, had better prognostic characteristics, such as lower Breslow and mitotic indexes as well as high lymphocytic infiltrate.

BRAF Gene and Melanoma: Back to the Future

As widely acknowledged, 40-50% of all melanoma patients harbour an activating BRAF mutation (mostly BRAF V600E). The identification of the RAS-RAF-MEK-ERK (MAP kinase) signalling pathway and its targeting has represented a valuable milestone for the advanced and, more recently, for the completely resected stage III and IV melanoma therapy management. However, despite progress in BRAF-mutant melanoma treatment, the two different approaches approved so far for metastatic disease, immunotherapy and BRAF+MEK inhibitors, allow a 5-year survival of no more than 60%, and most patients relapse during treatment due to acquired mechanisms of resistance. Deep insight into BRAF gene biology is fundamental to describe the acquired resistance mechanisms (primary and secondary) and to understand the molecular pathways that are now being investigated in preclinical and clinical studies with the aim of improving outcomes in BRAF-mutant patients.

Molecular Profiling of Merkel Cell Polyomavirus-Associated Merkel Cell Carcinoma and Cutaneous Melanoma

Merkel cell carcinoma (MCC) is a rare, high-grade, aggressive cutaneous neuroendocrine malignancy most commonly associated with sun-exposed areas of older individuals. A relatively newly identified human virus, the Merkel cell polyomavirus (MCPyV) has been implicated in the pathogenesis of MCC. Our study aimed to examine nine MCC cases and randomly selected 60 melanoma cases to identify MCPyV status and to elucidate genetic differences between virus-positive and -negative cases. Altogether, seven MCPyV-positive MCC samples and four melanoma samples were analyzed. In MCPyV-positive MCC RB1, TP53, FBXW7, CTNNB1, and HNF1A pathogenic variants were identified, while in virus-negative cases only benign variants were found. In MCPyV-positive melanoma cases, besides BRAF mutations the following genes were also affected: PIK3CA, STK11, CDKN2A, SMAD4, and APC. In contrast to studies found in the literature, a higher tumor burden was detected in virus-associated MCC compared to MCPyV-negative cases. No association was identified between virus infection and tumor burden in melanoma samples. We concluded that analyzing the key morphologic and immunohistological features of MCC is critical to avoid confusion with other cutaneous malignancies. Molecular genetic investigations such as next-generation sequencing (NGS) enable molecular stratification, which may have future clinical impact.

BRAF as a positive predictive biomarker: Focus on lung cancer and melanoma patients

In the era of personalized medicine, BRAF mutational assessment is mandatory in advanced-stage melanoma and non-small cell lung cancer (NSCLC) patients. The identification of actionable mutations is crucial for the adequate management of these patients. To date various drugs have been implemented in clinical practice. Similarly, various methods may be adopted for the identification of BRAF mutations. Here, we briefly review the current literature on BRAF in melanoma and NSCLC, focusing attention in particular on the different methods and drugs adopted in these patients. In addition, an overview of the real-world practice in different Italian laboratories with high expertise in molecular predictive pathology testing is provided.

Comparison of metagenomic next-generation sequencing technology, culture and GeneXpert MTB/RIF assay in the diagnosis of tuberculosis

Background

With a high incidence rate and mortality rate, tuberculosis (TB) is a major public health concern worldwide. There is an urgent need to develop the rapid, reliable and affordable diagnostic test for the detection of Mycobacterium tuberculosis (Mtb). Metagenomic next-generation sequencing (mNGS) showed promising values in the rapid diagnosis of clinical TB, while studies on the application of mNGS in pulmonary and extrapulmonary TB remain scarce.

Methods

In this study, we collected the results of both mNGS and culture of 70 specimens from suspected TB patients at the Shanghai Pulmonary Hospital of Tongji University. Results of GeneXpert MTB/RIF assay (Xpert) were obtained from 19 patients. We also assessed the diagnostic performance, relationship and consistency between mNGS, traditional culture method, and Xpert.

Results

Overall, 36 of 70 suspected patients were finally diagnosed with TB. The sensitivity, specificity, positive predictive value, negative predictive value and the Youden index of mNGS in all clinical TB specimens were calculated as 66.7% (95% CI: 0.489–0.809), 97.1% (95% CI: 0.829–0.998), 96.0% (95% CI: 0.777–0.998), 73.3% (95% CI: 0.578–0.849), 63.8%, respectively. The sensitivity of mNGS was much superior to that of conventional culture method (66.7%, 95% CI: 0.489–0.809 vs. 36.1%, 95% CI: 0.213–0.538) and Xpert (76.9%, 95% CI: 0.460–0.938 vs. 61.5%, 95% CI: 0.323–0.849). In pulmonary TB cases, mNGS, culture, and Xpert all demonstrated better diagnostic capacity for TB when compared with extrapulmonary TB cases. Among all methods and sample classifications, the Youden index of parallel diagnostic test in pulmonary samples was outstanding (mNGS/culture 88.2%; mNGS/Xpert 100%). Furthermore, the correlation and concordance between mNGS and culture method in all types of specimens was statistically significant (both P<0.001).

Conclusions

With high sensitivity and specificity, mNGS showed remarkable diagnostic performance in various samples from suspected TB patients. Combining mNGS and culture or Xpert method had the potential for clinical application in TB.

Implementation of an NGS panel for clinical practice in paraffin-embedded tissue samples from locally advanced and metastatic melanoma patients

Aim:

Single biomarker diagnostic test of BRAFV600 locus in metastatic melanoma is mandatory for treatment decision; however, multiple-gene based techniques, such as targeted next-generation sequencing (NGS) are being used to maximize the number of patients that can benefit from a targeted therapy. The main objective of this study is to investigate whether an NGS panel could be adopted in routine clinical care for advanced melanoma.

Methods:

Patients diagnosed with advanced melanoma at our center from 2017 to 2019 were included. Presence of genetic alterations was performed using two methods: real-time polymerase chain reaction-based Idylla test (Biocartis) and NGS with the oncomine solid tumor DNA kit (Thermo Fisher Scientific). Total genomic DNA was extracted from formalin-fixed and paraffin embedded samples for sequencing.

Results:

A total of 155 samples were evaluated for molecular analysis but 40 samples (25.8%) were inadequate for sequencing. The clinical utility of BRAFV600 real-time polymerase chain reaction and targeted-NGS was compared in 29 samples and a very good concordance was observed (Kappa = 0.89, 95% confidence interval 0.68 ± 1.05). An oncogenic mutation by NGS was found in 75 samples (65%)–53% of whom were candidates for personalized therapies. The most prevalent mutated genes were BRAF (39%), TP53 (23%), and NRAS (14%). Other genes identified at lower incidence (< 5%) were: PIK3CA, ERBB4, CTNNB1, STK11, FGFR1, SMAD4, KRAS, FGFR3, PTEN and AKT. Co-occurrence of oncogenic mutations was detected in 40% of the samples. Among the mutations identified, TP53 was significantly more prevalent in men (men 31.8% versus women 12.2%, P = 0.03) and NRAS in women (men 9.1% versus women 24.4%, P = 0.03).

Conclusions:

Targeted-NGS testing is a feasible technique to implement in the routine clinical practice. Based on our results, NGS has provided more information on target-genes than RT-PCR technique, maximizing the benefit for patients with advanced melanoma.

Decoding the Genomic Report for Radiologists

OBJECTIVE. The purpose of this review is to provide a guide for radiologists that explains the language and format of modern genomic reports and summarizes the relevance of this information for modern oncologic imaging. CONCLUSION. Genomic testing plays a critical role in guiding oncologic therapies in the age of targeted treatments. Understanding and interpreting genomic reports is a valuable skill for radiologists involved with oncologic imaging interpretation.

Detection of Gene Mutations in Liquid Biopsy of Melanoma Patients: Overview and Future Perspectives

OPINION STATEMENT

Liquid biopsies are still far from widely implanted in the clinical arena. Issues related to the added sensitivity of this test beyond conventional methods have not been fully resolved. Additionally, issues related to the specificity of these results especially as many cancers may share common mutation need further investigations. One way to resolve this may include the development and testing of large gene panels to add higher specificity. On the other hand, further studies are needed to support the idea that ctDNA or circulating tumor cells may constitute a better representation of the tumor subpopulation that is capable of metastasizing, which will strongly support its clinical value. Finally, survival studies showing a positive impact of this technology will also justify its widespread implementation in clinical practice.

Low BRAF V600 mutation prevalence in primary skin nodular melanoma in Indonesia: a real-time PCR detection among Javanese patients

BACKGROUND

Cutaneous melanoma is a rare, aggressive skin malignancy with a high mortality rate. Although only contributing 7.6% of the cases worldwide, Asia is responsible for 18.6% of deaths from cutaneous melanoma. BRAF V600 mutation presents a potential prognostic predictor in melanoma. Unfortunately, studies on that mutation in melanoma, particularly nodular subtype, in Indonesia are still scarce. This research aimed to investigate the prevalence of BRAF V600 mutation in primary skin nodular melanoma in Yogyakarta and Central Java, Indonesia. Its association with clinicopathological parameters was also analyzed.

METHODS

Forty paraffin-embedded tissue samples from primary skin nodular melanoma cases in 2011-2018 were collected from the two biggest referral hospitals in Yogyakarta and Central Java, Indonesia. The BRAF V600 mutation status was assessed using qualitative real-time PCR and its associations with age, sex, anatomic location, lymph node metastasis, tumor thickness, ulceration, mitotic index, necrosis, lymphovascular invasion, and tumor-infiltrating lymphocytes were analyzed.

RESULTS

BRAF V600 mutations were found in 4 (10%) samples. These mutations were significantly associated with the central (non-extremity) region (p = 0.013) and presence of lymphovascular invasion (p = 0.005). However, it was not associated with any other variables analyzed in this study.

CONCLUSION

The prevalence of BRAF V600 mutation in Indonesian primary skin nodular melanoma cases is low and significantly associated with anatomic location and lymphovascular invasion. It is lower than prevalences in other Asian populations as well as in Caucasian populations and suggests that melanoma cases in Javanese people may have distinct clinicopathological characteristics from other Asian ethnicities.

Analytical Evaluation of an NGS Testing Method for Routine Molecular Diagnostics on Melanoma Formalin-Fixed, Paraffin-Embedded Tumor-Derived DNA

Next Generation Sequencing (NGS) is a promising tool for the improvement of tumor molecular profiling in view of the identification of a personalized treatment in oncologic patients. To verify the potentiality of a targeted NGS (Ion AmpliSeq™ Cancer Hotspot Panel v2), selected melanoma samples (n = 21) were retrospectively analyzed on S5 platform in order to compare NGS performance with the conventional techniques adopted in our routine clinical setting (Sequenom MassARRAY system, Sanger sequencing, allele-specific real-time PCR). The capability in the identification of rare and low-frequency mutations in the main genes involved in melanoma (BRAF and NRAS genes) was verified and integrated with the results deriving from other oncogenes and tumor suppressor genes. The analytical evaluation was carried out by the analysis of DNA derived from control cell lines and FFPE (Formalin-Fixed, Paraffin-Embedded) samples to verify that the achieved resolution of uncommon mutations and low-frequency variants was suitable to meet the technical and clinical requests. Our results demonstrate that the amplicon-based NGS approach can reach the sensitivity proper of the allele-specific assays together with the high specificity of a sequencing method. An overall concordance among the tested methods was observed in the identification of classical and uncommon mutations. The assessment of the quality parameters and the comparison with the orthogonal methods suggest that the NGS method could be implemented in the clinical setting for melanoma molecular characterization.

Monitoring Melanoma Using Circulating Free DNA

Genetic material derived from tumours is constantly shed into the circulation of cancer patients both in the form of circulating free nucleic acids and within circulating cells or extracellular vesicles. Monitoring cancer-specific genomic alterations, particularly mutant allele frequencies, in circulating nucleic acids allows for a non-invasive liquid biopsy for detecting residual disease and response to therapy. The advent of molecular targeted treatments and immunotherapies with increasing effectiveness requires corresponding effective molecular biology methods for the detection of biomarkers such as circulating nucleic acid to monitor and ultimately personalise therapy. The use of polymerase chain reaction (PCR)-based methods, such as droplet digital PCR, allows for a very sensitive analysis of circulating tumour DNA, but typically only a limited number of gene mutations can be detected in parallel. In contrast, next-generation sequencing allows for parallel analysis of multiple mutations in many genes. The development of targeted next-generation sequencing cancer gene panels optimised for the detection of circulating free DNA now provides both the flexibility of multiple mutation analysis coupled with a sensitivity that approaches or even matches droplet digital PCR. In this review, we discuss the advantages and disadvantages of these current molecular technologies in conjunction with how this field is evolving in the context of melanoma diagnosis, prognosis, and monitoring of response to therapy.