Leptomeningeal disease in melanoma: An update on the developments in pathophysiology and clinical care

Survival improvements in patients with melanoma brain metastases and leptomeningeal disease in the modern era: Insights from a nationwide study (2015-2022)

INTRODUCTION

Advances in modern therapies have improved outcomes for patients with melanoma brain metastases (MBM), though prognosis remains poor. The optimal treatment strategy for patients who do not meet clinical trial inclusion criteria is unclear.

METHODS

This study included all patients with MBM diagnosed in Denmark between 2015 and 2022, identified through the Danish Metastatic Melanoma Database (DAMMED) and local surgical and radiotherapy records. Data were collected from electronic patient records.

RESULTS

A total of 838 patients were included, with a median overall survival (OS) of 9.0 months. Of these, 112 (19.4 %) survived beyond 3 years post-diagnosis. Patients treated with immune checkpoint inhibitors (ICI) as first line treatment, specifically ipilimumab + nivolumab, demonstrated an intracranial overall response rate (icORR) of 46 % and a 2-year OS of 49 %. Those treated with BRAF/MEK inhibitors (BRAF/MEKi) had an icORR of 56 % but a 2-year OS of 20 %. Patients with leptomeningeal disease (LMD, n = 67) had a median OS of 8.4 months. Systemic therapy was associated with a superior OS for patients with LMD, though no survival benefit was seen with ICI compared to BRAF/MEKi. Among the 230 patients who underwent surgery, 30 received postoperative stereotactic radiosurgery (SRS); however, there was no difference in OS or intracranial progression-free survival between the groups.

CONCLUSION

A considerable proportion of patients with brain metastases diagnosed after 2015 survived more than 3 years. Patients with LMD appeared to obtain limited benefit of ICI with only few patients alive > 3 years post-diagnosis.

Transcriptome analysis of novel B16 melanoma metastatic variants generated by serial intracarotid artery injection

The incidence of brain metastases (BrM) in patients with metastatic melanoma is reported to be 30-50% and constitutes the third most frequent BrM after breast and renal cancers. Treatment strategies including surgical resection, stereotactic radiation, and immunotherapy have improved clinical response rates and overall survival, but the changes that occur in circulating melanoma cells to promote invasion of the brain are not fully understood. To investigate brain tropism, we generated new variants of the B16 mouse melanoma model by serially passaging B16 cells through the brain of immune competent syngeneic C57BL/6 mice. Cells were injected into the right carotid artery and recovered from the brain after the mice had reached the study endpoint due to tumor burden, then expanded in vitro and reinjected. We compared the transcriptomes of 4th generation B16 cell populations from separate lineages with the founder B16-F0 cells. Gene set enrichment analysis (GSEA) of differentially expressed protein coding genes revealed that cells isolated from the brain as well as from the lung and meninges expressed higher levels of genes associated with an epithelial to mesenchymal transition (EMT), upregulation of the KRAS signaling pathway, and a metastasis aggressiveness gene signature associated with poor survival in melanoma patients. Principal component analysis of differentially expressed genes showed that 4th generation melanoma cells isolated from the brain, lung and meninges from one lineage were distinct from those of the other three lineages. Among the differentially expressed genes, transcript levels of several genes, including Itgb2, Rftn2, and Kcnn4, were significantly higher in all cell populations that comprised this lineage compared with all cell populations from the other three lineages. In conclusion, we have derived an aggressive, highly brain metastatic B16 variant associated with leptomeningeal disease by serially passaging cells in vivo.

Survival and treatment outcomes in patients with leptomeningeal disease from metastatic melanoma

Background

Melanoma leptomeningeal disease (LMD) has a poor prognosis. However, the management of patients with advanced melanoma has evolved with time, including those with LMD. We reviewed a large cohort of melanoma LMD patients to assess factors associated with survival.

Methods

Retrospective clinical data was collected on patients diagnosed with LMD at MD Anderson Cancer Center from 2015 to 2020. Overall survival (OS) was determined from LMD diagnosis to date of death or last follow-up. The Kaplan-Meier method and log-rank test were used to estimate OS and to assess univariate group differences, respectively. Multivariable associations of survival with variables of interest were determined using Cox proportional hazards regression models.

Results

A total of 172 patients were identified. The median age at LMD diagnosis was 53 (range 20-79) years, and all patients had radiographic evidence of LMD on magnetic resonance imaging of either brain or spine. In total 143 patients previously received systemic therapy (83%), with a median of 2 prior treatments (range 0-5). 81 patients (47%) had concurrent uncontrolled systemic disease and 80 patients (53%) had elevated serum LDH at the time of diagnosis. With a median follow-up of 4.0 months (range 0.1-65.3 months), median OS for all patients from LMD diagnosis was 4.9 months. Patients (n = 45) who received intrathecal therapy or systemic immunotherapy for LMD had a median OS of 8.0 months and 10.2 months, respectively. On multivariable analysis, decreased performance status, positive CSF cytology, elevated LDH, and whole brain radiation were associated with worse OS.

Conclusions

Despite many advances in therapeutic options, the outcomes of melanoma patients with LMD remains poor. However, a subset of patients appears to derive benefit from LMD-directed treatment.

Branched-chain keto acids promote an immune-suppressive and neurodegenerative microenvironment in leptomeningeal disease

Leptomeningeal disease (LMD) occurs when tumors seed into the leptomeningeal space and cerebrospinal fluid (CSF), leading to severe neurological deterioration and poor survival outcomes. We utilized comprehensive multi-omics analyses of CSF from patients with lymphoma LMD to demonstrate an immunosuppressive cellular microenvironment and identified dysregulations in proteins and lipids indicating neurodegenerative processes. Strikingly, we found a significant accumulation of toxic branched-chain keto acids (BCKA) in the CSF of patients with LMD. The BCKA accumulation was found to be a pan-cancer occurrence, evident in lymphoma, breast cancer, and melanoma LMD patients. Functionally, BCKA disrupted the viability and function of endogenous T lymphocytes, chimeric antigen receptor (CAR) T cells, neurons, and meningeal cells. Treatment of LMD mice with BCKA-reducing sodium phenylbutyrate significantly improved neurological function, survival outcomes, and efficacy of anti-CD19 CAR T cell therapy. This is the first report of BCKA accumulation in LMD and provides preclinical evidence that targeting these toxic metabolites improves outcomes.