Evolving Treatment Approaches to Mucosal Melanoma

Combination Immunotherapy for Mucosal Melanoma: Molecular Mechanism, Research Status, and Future Directions

OPINION STATEMENT

Mucosal melanoma is a rare and aggressive subtype of melanoma, accounting for 1%-2% of new cases in the United States in 2023, and 20%-30% in China and other Asian countries. Its origin is often occult, with the lack of early clinical features, the absence of actionable driver mutations, and poor response to immunotherapy, all contributing to its poor prognosis. The rarity of this subtype leads to limited awareness and interventions. Furthermore, due to its immune evasion mechanisms, mucosal melanoma shows resistance to traditional immune checkpoint inhibitors. Consequently, new therapeutic strategies are urgently needed to improve patient outcomes. Recent clinical trials have suggested that combination immunotherapy can overcome immune evasion, reduce resistance to treatment, produce synergistic anti-tumor effects, and improve survival. Epidemiological factors and clinical characteristics play significant roles in diagnosis and prognosis, while the mutational landscape influences responses to immunotherapy. This review provides an overview of these aspects and systematically discusses current research on combination therapies and emerging immunotherapy approaches for mucosal melanoma. It also explores potential future directions for treatment, aiming to enhance therapeutic strategies for this rare cancer and improve patient outcomes.

Distinct Transcriptomic and Tumor Microenvironment Profiles in Sinonasal Mucosal Melanoma and Aggressive Cutaneous Melanomas

Background/Objectives: Sinonasal mucosal melanoma (SNMM) is a rare and aggressive melanoma subtype with a notably poor prognosis compared to cutaneous melanoma (CM). Despite advances in molecular characterization, SNMM remains underexplored, posing a clinical challenge and highlighting the need for detailed molecular profiling. This study aimed to identify the molecular features of SNMM, elucidate its clinical behavior and prognostic implications, and provide insights for improved therapeutic strategies. Methods: This retrospective study analyzed 37 primary melanoma tumors diagnosed at the Hospital Clinic of Barcelona. Gene expression was examined using 1402 immuno-oncology-related probes through next-generation sequencing. Hierarchical clustering analysis (HCA), differentially expressed genes (DEGs), gene set enrichment analysis (GSEA), and the xCell algorithm were performed. The statistical methods comprised descriptive statistics, clinical variable associations, and survival analyses. Results: HCA revealed two primary clusters. Cluster A exclusively contained CM tumors (20/24), while cluster B included all SNMMs (13/13) and some CMs (4/24). Cluster B showed a higher average age at diagnosis (p = 0.018), higher mitotic index (p = 0.0478), fewer BRAF mutations (p = 0.0017), and poorer melanoma-specific survival (p = 0.0029). Cluster B showed 602 DEGs with cell cycle pathways enriched, immune pathways diminished, lower immune scores (p < 0.0001), and higher stromal scores (p = 0.0074). Conclusions: This study revealed distinct molecular characteristics and an altered tumor microenvironment in SNMMs and certain aggressive CMs. Identifying specific genes and pathways involved in cell cycle progression and immune evasion suggests potential prognostic markers, offering new avenues for enhancing treatment strategies and improving patient survival rates.

MET amplification correlates with poor prognosis and immunotherapy response as a subtype of melanoma: a multicenter retrospective study

BACKGROUND

Mesenchymal epithelial transition factor (MET) variant is an independent prognostic factor for worse prognosis in patients with lung cancer or gastroesophageal adenocarcinoma. MET gene variants can be regarded as a subtype of melanoma but there is a lack of studies regarding the frequency of MET genetic alterations and the efficacy of immunotherapy in melanoma patients. The purpose of this study is to explore potential therapeutic strategies for melanoma subtypes with MET alterations.

METHODS

A total of 1751 malignant melanomas were analyzed to illustrate the landscape of MET mutations. We collected 55 melanoma cases from multicenter for a retrospective cohort from 2010 to 2023. We analyzed the impact of MET amplification on the efficacy of immunotherapy in the retrospective cohort after propensity score matching (PSM) and a pancancer cohort. CIBERSORT was used to evaluate the immune infiltration.

RESULTS

There were no instances of MET 14 exon skipping, and only instances of MET amplification were found in the 1751 melanomas and our retrospective cohort. Cox proportional hazards model analysis showed that MET amplification (P = 0.006) was significantly associated with poorer overall survival (OS) in patients who received immunotherapy as the first-line treatment. Compared with patients with MET amplification, patients in the negative control (NC) group had a significantly better OS (P = 0.022) after PSM. Analysis of 1661 pancancer cases with the MSK-IMPACT assay showed that patients receiving immunotherapy in the MET amplification group had a trend toward worse OS than those without MET amplification (P = 0.025).

CONCLUSIONS

This database analysis showed that the main type of MET mutation is amplification in malignant melanoma. MET-amplified solid tumors might be considered for targeted therapy, as MET amplification can be regarded as a risk factor affecting the prognosis of patients with tumors treated with immunotherapy.

A Retrospective Analysis of the Prognostic Factors and Adverse Events in the Treatment of Mucosal Melanoma in a Single Centre

Background: Despite the dramatic advances in the management of metastatic cutaneous melanoma, there remains no consensus-based, evidence-based strategy for the management of mucosal melanoma. The rare nature of the disease, its late clinical presentation, and distinct tumour biology all complicate efforts to optimise patient outcomes. Methods: To this end, we carried out a monocentric, retrospective analysis of all patients diagnosed with mucosal melanoma and treated between 2013 and 2021. Both tumour- and patient-specific characteristics were recorded, in addition to immune-related adverse events, in order to provide real-world data on disease progression, treatment efficacy, and the identification of prognostic markers. Results: A total of 20 patients were identified (14 females and 6 males), with a mean age at diagnosis of 65.9 years. The median follow-up was 3.9 years (95% CI 1.4-6.4 years) from the initiation of systemic therapy. The median OS in the entire cohort was 1.9 years (95% CI 0.5-3.3 years). Performance status, sex, body mass index, and the presence of brain metastases were not associated with poorer outcomes. However, serum lactate dehydrogenase levels (LDH) (p = 0.04) and an NRAS mutation were markers of a poor prognosis (p = 0.004). Conclusuion: There is a pressing need for real-world, prospective, and clinical trial data to inform the optimal management of mucosal melanoma, and data supporting the use of adjuvant and neo-adjuvant immunotherapy are currently lacking. However, an elevated LDH is a reliable, independent negative prognostic marker. Inter-disciplinary management remains essential in order to develop optimal treatment strategies.

A Whole-Transcriptomic Analysis of Canine Oral Melanoma: A Chance to Disclose the Radiotherapy Effect and Outcome-Associated Gene Signature

Oral melanoma (OM) is the most common malignant oral tumour among dogs and shares similarities with human mucosal melanoma (HMM), validating the role of canine species as an immunocompetent model for cancer research. In both humans and dogs, the prognosis is poor and radiotherapy (RT) represents a cornerstone in the management of this tumour, either as an adjuvant or a palliative treatment. In this study, by means of RNA-seq, the effect of RT weekly fractionated in 9 Gray (Gy), up to a total dose of 36 Gy (4 weeks), was evaluated in eight dogs affected by OM. Furthermore, possible transcriptomic differences in blood and biopsies that might be associated with a longer overall survival (OS) were investigated. The immune response, glycosylation, cell adhesion, and cell cycle were the most affected pathways by RT, while tumour microenvironment (TME) composition and canonical and non-canonical WNT pathways appeared to be modulated in association with OS. Taking these results as a whole, this study improved our understanding of the local and systemic effect of RT, reinforcing the pivotal role of anti-tumour immunity in the control of canine oral melanoma (COM).

Clinical Characteristics and Special Considerations in the Management of Rare Melanoma Subtypes

Rare histologic subtypes of melanoma, including acral, mucosal, uveal, and desmoplastic melanomas, only make up 5% of all diagnosed melanomas and are often underrepresented in large, randomized trials. Recent advancements in systemic therapy have shown marked improvement in pathologic response rates, improving progression-free and overall survival among cutaneous melanoma patients, but there are limited data to demonstrate improved survival among rarer subtypes of melanoma. Acral melanoma has a poor response to immunotherapy and is associated with worse survival. Mucosal melanoma has a large variability in its presentation, a poor prognosis, and a low mutational burden. Uveal melanoma is associated with a high rate of liver metastasis; recent adoption of infusion and perfusion therapies has demonstrated improved survival among these patients. Desmoplastic melanoma, a high-risk cutaneous melanoma, is associated with high locoregional recurrence rates and mutational burden, suggesting this melanoma may have enhanced response to immunotherapy. While these variants of melanoma represent distinct disease entities, this review highlights the clinicopathologic characteristics and treatment recommendations for each of these rare melanomas and highlights the utility of modern therapies for each of them.

Primary non-cutaneous melanomas of the head and neck: Case series and review of the literature

Primary non-cutaneous melanoma is a rare type of melanoma that occurs mostly on mucosal surfaces. The head and neck region is the most common site for these melanomas. The following cases described herein include patients diagnosed with primary non-cutaneous melanomas. The locations included the parotid gland (one case), the submandibular gland (one case), and the nasal cavity and paranasal sinuses (three cases). Among these patients, one patient developed lymph node metastasis and one patient had distant metastasis. Treatment included endoscopic surgery (one case), endoscopic surgery with adjuvant radiotherapy (one case), open surgery (one case), and palliative chemotherapy (one case). One patient refused to receive treatment. After treatment, one patient had local recurrence. A local and distant recurrence was noted in one case. This report aims to describe clinical features, treatment options, and prognosis of primary non-cutaneous melanomas of the head and neck.

Comparative Epigenetic Profiling Reveals Distinct Features of Mucosal Melanomas Associated with Immune Cell Infiltration and Their Clinical Implications

Mucosal melanoma exhibits limited responsiveness to anti-PD-1 therapy. However, a subgroup of mucosal melanomas, particularly those situated at specific anatomic sites like primary malignant melanoma of the esophagus (PMME), display remarkable sensitivity to anti-PD-1 treatment. The underlying mechanisms driving this superior response and the DNA methylation patterns in mucosal melanoma have not been thoroughly investigated. We collected tumor samples from 50 patients with mucosal melanoma, including 31 PMME and 19 non-esophageal mucosal melanoma (NEMM). Targeted bisulfite sequencing was conducted to characterize the DNA methylation landscape of mucosal melanoma and explore the epigenetic profiling differences between PMME and NEMM. Bulk RNA sequencing and multiplex immunofluorescence staining were performed to confirm the impact of methylation on gene expression and immune microenvironment. Our analysis revealed distinct epigenetic signatures that distinguish mucosal melanomas of different origins. Notably, PMME exhibited distinct epigenetic profiling characterized by a global hypermethylation alteration compared with NEMM. The prognostic model based on the methylation scores of a 7-DMR panel could effectively predict the overall survival of patients with PMME and potentially serve as a prognostic factor. PMME displayed a substantial enrichment of immune-activating cells in contrast to NEMM. Furthermore, we observed hypermethylation of the TERT promoter in PMME, which correlated with heightened CD8+ T-cell infiltration, and patients with hypermethylated TERT were likely to have improved responses to immunotherapy. Our results indicated that PMME shows a distinct methylation landscape compared with NEMM, and the epigenetic status of TERT might be used to estimate prognosis and direct anti-PD-1 treatment for mucosal melanoma.

SIGNIFICANCE

This study investigated the intricate epigenetic factor of mucosal melanomas contributed to the differential immune checkpoint inhibitor response, and found that PMME exhibited a global hypermethylation pattern and lower gene expression in comparison to NEMM. TERT hypermethylation may contribute to the favorable responses observed in patients with mucosal melanoma undergoing immunotherapy.

Mucosal Melanoma Clinical Management and Prognostic Implications: A Retrospective Cohort Study

Mucosal melanoma (MM) is an uncommon melanoma subtype affecting mucosal surfaces of the head and neck, anorectal region, and vulvovaginal area. We aimed to present our experience at a tertiary-level hospital regarding MM diagnosis, management, monitoring of progression, mutations, and outcome predictors. We performed a registry-based cohort study including MM cases diagnosed from 2012 to 2022 and retrospectively characterized somatic mutations on BRAF, NRAS and c-KIT. We employed Kaplan-Meier curves, log-rank tests, and Cox regression analysis to explore prognostic factors and survival outcomes in a cohort of 35 patients, mainly women (63%) with a median age of 70 years. Predominantly, MM occurred in the vulvovaginal region (48.6%). At diagnosis, 28.6% had lymph node involvement, and 31.4% also had distant metastasis. Mutations in BRAF and c-KIT were identified in 3/35 (9%) and 2/6 patients (33%), respectively. Surgery was performed in 71.4% of patients, and most received systemic treatment (65.7%). Lower disease stage, thinner Breslow depth, and surgical resection were associated with improved overall survival. Notably, age, sex, radiotherapy, and BRAF mutant status did not affect survival. Standard management typically involves immunotherapy. Cases with BRAF or c-KIT mutations may be considered for targeted therapies. Unfortunately, MM prognosis remains unfavorable, with a less than 50% survival rate at 2 years.

A human mucosal melanoma organoid platform for modeling tumor heterogeneity and exploring immunotherapy combination options

Mucosal melanoma (MM), an aggressive rare subtype of melanoma, is distinct from cutaneous melanoma and has poor prognoses. We addressed the lack of cell models for MM by establishing 30 organoids of human oral MM (OMM), which retained major histopathological and functional features of parental tumors. Organoid groups derived from chronologically or intratumorally distinct lesions within the same individual displayed heterogeneous genetics, expression profiles, and drug responses, indicating rapid tumor evolution and poor clinical response. Furthermore, transcriptome analysis revealed receptor tyrosine kinases (RTKs) signaling, particularly NGFR, a nerve growth factor receptor, was significantly up-regulated in OMMs and organoids from patients resistant to anti-programmed cell death protein 1 (anti-PD-1) therapy. Combining anti-PD-1 with anlotinib (a phase 2 multitarget RTK inhibitor for OMM) or NGFR knockdown enhanced the effective activity of immune cells in organoid-immune cell coculture systems. Together, our study suggested that OMM organoids serve as faithful models for exploring tumor evolution and immunotherapy combination strategies.

Clinical significance of genetic profiling based on different anatomic sites in patients with mucosal melanoma who received or did not receive immune checkpoint inhibitors

BACKGROUND

To date, data on the efficacy of targeted therapies for mucosal melanoma (MM) are limited. In this study, we analyzed genetic alterations according to the primary site of origin, which could provide clues for targeted therapy for MM.

METHODS

We conducted a retrospective cohort study of 112 patients with MM. Targeted sequencing was performed to analyze genetic aberrations. Kaplan-Meier analysis was conducted with the log-rank test to compare the significance among subgroups.

RESULTS

In total, 112 patients with MM were included according to the anatomic sites: 38 (33.9%) in the head and neck, 22 (19.6%) in the genitourinary tract, 21 (18.8%) in the anorectum, 19 (17.0%) in the esophagus, 10 (8.9%) in the uvea, and 2 (1.8%) in the small bowel. The most significantly mutated genes included BRAF (17%), KIT (15%), RAS (15%), TP53 (13%), NF1 (12%), SF3B1 (11%), GNA11 (7%), GNAQ (5%), and FBXW7 (4%). A large number of chromosomal structural variants was found. The anatomic sites of esophagus and small bowel were independent risk factors for progression-free survival (PFS, hazard ratio [HR] 4.78, 95% confidence interval [CI] 2.42-9.45, P < 0.0001) and overall survival (OS, HR 5.26, 95% CI 2.51-11.03, P < 0.0001). Casitas B-lineage lymphoma (CBL) mutants showed significantly poorer PFS and OS. In contrast, MM patients who received immune checkpoint inhibitors (ICIs) had a significantly more favorable OS (HR 0.39, 95% CI 0.20-0.75, P = 0.008).

CONCLUSIONS

Our findings reveal the genetic features of patients with MM, mainly across six anatomic sites, offering a potential avenue for targeted therapies.

Primary Mucosal Melanoma of the Lip With GNA11 Mutation in a 23-Year-Old Pregnant Woman

Mucosal melanoma represents a small proportion of all melanoma cases and is associated with a worse prognosis. Primary malignant melanoma of the lip (PMML) is far less common, and only a few cases have been reported since 1997, most commonly in China, Japan, Uganda, and India. Most of these cases have been associated with the gene C-KIT. As a result, treatment guidelines surrounding mucosal melanoma are unclear, especially in complicated populations such as pregnant women. Mutations in theGNAQ and GNA11 genes have been found to be associated with uveal melanoma, while they are rarely associated with mucosal melanoma. We present the case of a 23-year-old pregnant woman who was found to have likely primary malignant melanoma of the lip that metastasized to the left jaw, neck, breast, lungs, and ovaries and was found to be positive for both the BRAF-MLL3 and GNA11 mutation.

Current Trends in Mucosal Melanomas: An Overview

Primary mucosal melanomas (MMs) are uncommon tumors originating from melanocytes located in the mucous membranes at various anatomic sites within the body. MM significantly differs from cutaneous melanoma (CM) regarding epidemiology, genetic profile, clinical presentation, and response to therapies. Despite these differences, that have important implications for both disease diagnosis and prognosis, MMs are usually treated in the same way as CM but exhibit a lower response rate to immunotherapy leading to a poorer survival rate. Furthermore, a high inter-patient variability can be observed in relation to therapeutic response. Recently, novel "omics" techniques have evidenced that MM lesions have different genomic, molecular, and metabolic landscapes as compared with CM lesions, thus explaining the heterogeneity of the response. Such specific molecular aspects might be useful to identify new biomarkers aimed at improving the diagnosis and selection of MM patients who could benefit from immunotherapy or targeted therapy. In this review, we have focused on relevant molecular and clinical advancements for the different MM subtypes in order to describe the updated knowledge relating to main diagnostic, clinical, and therapeutic implications as well as to provide hints on likely future directions.

Neoadjuvant checkpoint inhibitor immunotherapy for resectable mucosal melanoma

Background

Neoadjuvant checkpoint inhibition (CPI) has recently demonstrated impressive outcomes in patients with stage 3 cutaneous melanoma. However, the safety, efficacy, and outcome of neoadjuvant CPI in patients with mucosal melanoma (MM) are not well studied as MM is a rare melanoma subtype. CPI such as combination nivolumab and ipilimumab achieves response rates of 37-43% in unresectable or metastatic MM but there is limited data regarding the efficacy of these agents in the preoperative setting. We hypothesize that neoadjuvant CPI is a safe and feasible approach for patients with resectable MM.

Method

Under an institutionally approved protocol, we identified adult MM patients with resectable disease who received neoadjuvant anti-PD1 +/- anti-CTLA4 between 2015 to 2019 at our institution. Clinical information include age, gender, presence of nodal involvement or satellitosis, functional status, pre-treatment LDH, tumor mutation status, and treatment data was collected. Outcomes include event free survival (EFS), overall survival (OS), objective response rate (ORR), pathologic response rate (PRR), and grade ≥3 toxicities.

Results

We identified 36 patients. Median age was 62; 58% were female. Seventy-eight percent of patients received anti-PD1 + anti-CTLA4. Node positive disease or satellite lesions was present at the time of treatment initiation in 47% of patients. Primary sites of disease were anorectal (53%), urogenital (25%), head and neck (17%), and esophageal (6%). A minority of patients did not undergo surgery due to complete response (n=3, 8%) and disease progression (n=6, 17%), respectively. With a median follow up of 37.9 months, the median EFS was 9.2 months with 3-year EFS rate of 29%. Median OS had not been reached and 3-year OS rate was 55%. ORR was 47% and PRR was 35%. EFS was significantly higher for patients with objective response and for patients with pathologic response. OS was significantly higher for patients with pathologic response. Grade 3 toxicities were reported in 39% of patients.

Conclusion

Neoadjuvant CPI for resectable MM is a feasible approach with signs of efficacy and an acceptable safety profile. As there is currently no standard approach for resectable MM, this study supports further investigations using neoadjuvant therapy for these patients.