Ex Vivo Culture of Circulating Tumor Cells in the Cerebral Spinal Fluid from Melanoma Patients to Study Melanoma-Associated Leptomeningeal Disease

Melanoma-associated leptomeningeal disease (M-LMD) occurs when circulating tumor cells (CTCs) enter into the cerebral spinal fluid (CSF) and colonize the meninges, the membrane layers that protect the brain and the spinal cord. Once established, the prognosis for M-LMD patients is dismal, with overall survival ranging from weeks to months. This is primarily due to a paucity in our understanding of the disease and, as a consequence, the availability of effective treatment options. Defining the underlying biology of M-LMD will significantly improve the ability to adapt available therapies for M-LMD treatment or design novel inhibitors for this universally fatal disease. A major barrier, however, lies in obtaining sufficient quantities of CTCs from the patient-derived CSF (CSF-CTCs) to conduct preclinical experiments, such as molecular characterization, functional analysis, and in vivo efficacy studies. Culturing CSF-CTCs ex vivo has also proven to be challenging. To address this, a novel protocol for the culture of patient-derived M-LMD CSF-CTCs ex vivo and in vivo is developed. The incorporation of conditioned media produced by human meningeal cells (HMCs) is found to be critical to the procedure. Cytokine array analysis reveals that factors produced by HMCs, such as insulin-like growth factor-binding proteins (IGFBPs) and vascular endothelial growth factor-A (VEGF-A), are important in supporting CSF-CTC survival ex vivo. Here, the usefulness of the isolated patient-derived CSF-CTC lines is demonstrated in determining the efficacy of inhibitors that target the insulin-like growth factor (IGF) and mitogen-activated protein kinase (MAPK) signaling pathways. In addition, the ability to intrathecally inoculate these cells in vivo to establish murine models of M-LMD that can be employed for preclinical testing of approved or novel therapies is shown. These tools can help unravel the underlying biology driving CSF-CTC establishment in the meninges and identify novel therapies to reduce the morbidity and mortality associated with M-LMD.

Clinical outcomes of melanoma brain metastases treated with nivolumab and ipilimumab alone versus nivolumab and ipilimumab with stereotactic radiosurgery

PURPOSE

Upfront dual checkpoint blockade with immune checkpoint inhibitors (ICI) has demonstrated efficacy for treating melanoma brain metastases (MBM) in asymptomatic patients. Whether the combination of stereotactic radiosurgery (SRS) with dual checkpoint blockade improves outcomes over dual-checkpoint blockade alone is unknown. We evaluated clinical outcomes of patients with MBM receiving ICI with nivolumab and ipilimumab, with and without SRS.

METHODS

49 patients with 158 MBM receiving nivolumab and ipilimumab for untreated MBM between 2015 and 2022 were identified at our institution. Patient and tumor characteristics including age, Karnofsky Performance Status (KPS), presence of symptoms, cancer history, MBM burden, and therapy course were recorded. Outcomes measured from initiation of MBM-directed therapy included overall survival (OS), local control (LC), and distant intracranial control (DIC). Time-to-event analysis was conducted with the Kaplan-Meier method.

RESULTS

25 patients with 74 MBM received ICI alone, and 24 patients with 84 MBM received concurrent SRS. Median follow-up was 24 months. No differences in age (p = 0.96), KPS (p = 0.85), presence of symptoms (p = 0.79), prior MBM (p = 0.68), prior MBM-directed surgery (p = 0.96) or SRS (p = 0.68), MBM size (p = 0.67), or MBM number (p = 0.94) were seen. There was a higher rate of nivolumab and ipilimumab course completion in the SRS group (54% vs. 24%; p = 0.029). The SRS group received prior immunotherapy more often than the ICI alone group (54% vs. 8.0%; p < 0.001). There was no significant difference in 1-year OS (72% vs. 71%, p = 0.20) and DIC (63% v 51%, p = 0.26) between groups. The SRS group had higher 1-year LC (92% vs. 64%; p = 0.002). On multivariate analysis, LC was improved with combination therapy (AHR 0.38, p = 0.01).

CONCLUSION

In our analysis, patients who received SRS with nivolumab and ipilimumab had superior LC without increased risk of toxicity or compromised immunotherapy treatment completion despite the SRS cohort having higher rates of prior immunotherapy. Further prospective study of combination nivolumab and ipilimumab with SRS is warranted.

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

Leptomeningeal disease (LMD) remains a major challenge in the clinical management of metastatic melanoma patients. Outcomes for patient remain poor, and patients with LMD continue to be excluded from almost all clinical trials. However, recent trials have demonstrated the feasibility of conducting prospective clinical trials in these patients. Further, new insights into the pathophysiology of LMD are identifying rational new therapeutic strategies. Here we present recent advances in the understanding of, and treatment options for, LMD from metastatic melanoma. We also annotate key areas of future focus to accelerate progress for this challenging but emerging field.

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.

Differential requirements for CD4+ T cells in the efficacy of the anti-PD-1+LAG-3 and anti-PD-1+CTLA-4 combinations in melanoma flank and brain metastasis models

BACKGROUND

Although the anti-PD-1+LAG-3 and the anti-PD-1+CTLA-4 combinations are effective in advanced melanoma, it remains unclear whether their mechanisms of action overlap.

METHODS

We used single cell (sc) RNA-seq, flow cytometry and IHC analysis of responding SM1, D4M-UV2 and B16 melanoma flank tumors and SM1 brain metastases to explore the mechanism of action of the anti-PD-1+LAG-3 and the anti-PD-1+CTLA-4 combination. CD4+ and CD8+ T cell depletion, tetramer binding assays and ELISPOT assays were used to demonstrate the unique role of CD4+T cell help in the antitumor effects of the anti-PD-1+LAG-3 combination.

RESULTS

The anti-PD-1+CTLA-4 combination was associated with the infiltration of FOXP3+regulatory CD4+ cells (Tregs), fewer activated CD4+T cells and the accumulation of a subset of IFNγ secreting cytotoxic CD8+T cells, whereas the anti-PD-1+LAG-3 combination led to the accumulation of CD4+T helper cells that expressed CXCR4, TNFSF8, IL21R and a subset of CD8+T cells with reduced expression of cytotoxic markers. T cell depletion studies showed a requirement for CD4+T cells for the anti-PD-1+LAG-3 combination, but not the PD-1-CTLA-4 combination at both flank and brain tumor sites. In anti-PD-1+LAG-3 treated tumors, CD4+T cell depletion was associated with fewer activated (CD69+) CD8+T cells and impaired IFNγ release but, conversely, increased numbers of activated CD8+T cells and IFNγ release in anti-PD-1+CTLA-4 treated tumors.

CONCLUSIONS

Together these studies suggest that these two clinically relevant immune checkpoint inhibitor (ICI) combinations have differential effects on CD4+T cell polarization, which in turn, impacted cytotoxic CD8+T cell function. Further insights into the mechanisms of action/resistance of these clinically-relevant ICI combinations will allow therapy to be further personalized.

HDAC8-mediated inhibition of EP300 drives a transcriptional state that increases melanoma brain metastasis

Melanomas can adopt multiple transcriptional states. Little is known about the epigenetic drivers of these cell states, limiting our ability to regulate melanoma heterogeneity. Here, we identify stress-induced HDAC8 activity as driving melanoma brain metastasis development. Exposure of melanocytes and melanoma cells to multiple stresses increases HDAC8 activation leading to a neural crest-stem cell transcriptional state and an amoeboid, invasive phenotype that increases seeding to the brain. Using ATAC-Seq and ChIP-Seq we show that increased HDAC8 activity alters chromatin structure by increasing H3K27ac and enhancing accessibility at c-Jun binding sites. Functionally, HDAC8 deacetylates the histone acetyltransferase EP300, causing its enzymatic inactivation. This, in turn, increases binding of EP300 to Jun-transcriptional sites and decreases binding to MITF-transcriptional sites. Inhibition of EP300 increases melanoma cell invasion, resistance to stress and increases melanoma brain metastasis development. HDAC8 is identified as a mediator of transcriptional co-factor inactivation and chromatin accessibility that drives brain metastasis.

Stereotactic radiosurgery and anti-PD-1 + CTLA-4 therapy, anti-PD-1 therapy, anti-CTLA-4 therapy, BRAF/MEK inhibitors, BRAF inhibitors, or conventional chemotherapy for the management of melanoma brain metastases

BACKGROUND

Immunotherapy and targeted BRAF/MEK inhibitors (i) have revolutionised the systemic management of advanced melanoma. Given the role of stereotactic radiosurgery (SRS) in the local management of brain metastases, we sought to evaluate clinical outcomes in patients with melanoma brain metastases (MBM) treated with SRS and various systemic therapies.

METHODS

Patients were included if MBM were diagnosed and treated with SRS within 3 months of receiving anti-PD-1+CTLA-4 therapy, anti-PD-1 therapy, anti-CTLA-4 therapy, BRAF/MEK-i, BRAF-i, or conventional chemotherapy. Comparisons between groups were made for overall survival (OS), distant MBM control, local MBM, systemic progression-free survival (sPFS), and neurotoxicity.

RESULTS

In total, 257 patients with 1048 MBM treated over 368 SRS sessions between 2011 and 2020 were identified. On MVA, treatment with anti-PD1+anti-CTLA-4, anti-PD-1, and BRAF/MEK-i improved distant intracranial control over conventional chemotherapy. No significant differences were noted in local control (LC) between groups (p = 0.78). Kaplan-Meier OS at 12 months for anti-PD-1 + CTLA-4 therapy, anti-PD-1 therapy, anti-CTLA-4 therapy, BRAF/MEK-i, BRAF-i, and conventional chemotherapy was 68%, 59%, 45%, 62%, 21%, and 15%, respectively (p = <0.0001). The sPFS rates at 12 months were 57%, 53%, 42%, 45%, 14%, and 6% (p = <0.0001). No significant differences were noted in rates of radiation necrosis (p = 0.93).

CONCLUSIONS

This is among the largest series evaluating MBM treated with SRS and various systemic therapy regimens. Our analysis noted significant differences in OS, distant MBM control, and sPFS by systemic therapy. No differences in LC or radiation necrosis risk were noted.

Tucatinib and stereotactic radiosurgery in the management of HER2 positive breast cancer brain metastases

PURPOSE

HER2-positive breast cancer has a high risk of brain metastasis. Stereotactic radiosurgery (SRS) is standard of care for limited brain metastases. Tucatinib, a HER2-targeted tyrosine kinase inhibitor, has demonstrated intracranial efficacy in the HER2-CLIMB Trial. However, it is unknown whether tucatinib with SRS is safe or effective.

METHODS

A retrospective analysis of HER2-positive breast cancer treated with SRS and tucatinib for brain metastases management was performed. All patients received tucatinib and SRS for the management of active brain metastases. The primary endpoint was local and distant brain tumor control. Secondary endpoints were intracranial progression free survival (CNS-PFS), systemic PFS, overall survival (OS), and neurotoxicity.

RESULTS

A total of 135 lesions treated with SRS over 39 treatment sessions in 22 patients were identified. Median follow-up from tucatinib initiation was 20.8 months. Local brain control was 94% at 12-months and 81% at 24-months. Distant brain control was 39% at 12-months and 26% at 24-months. Median survival was 21.2 months, with 12- and 24-month OS rates of 84% and 50%, respectively. Median CNS-PFS was 11.3 months, with 12- and 24-month CNS-PFS rates of 44.9% at both time points. Median systemic PFS was not reached, with 12- and 24-month systemic PFS rates of 86% and 57%, respectively. Symptomatic radiation necrosis occurred in 6 (4%) lesions. No additional unexpected toxicities were noted.

CONCLUSIONS

SRS in combination with tucatinib, capecitabine, and trastuzumab appears to be a safe and feasible treatment for HER2 + brain metastases. Further prospective evaluation of potential synergistic effects is warranted.

A Brain, A Heart, and the Courage: Balancing Benefit and Toxicity of Immunotherapy in Melanoma

The overall survival of advanced melanoma has improved dramatically. Immunotherapies, specifically checkpoint inhibitors, have played a large role in this improvement. These agents have also shown benefit in the adjuvant setting, are approved for treatment of resected stage II, III, and IV melanoma, and play an evolving role in the neoadjuvant setting. Although generally well tolerated, immune-related adverse events occur and can be severe. Here we focus on some severe and potentially long term toxicities, including cardiovascular and neurologic toxicities. Our understanding of the acute and long-term toxicities of immune checkpoint inhibitors continues to evolve. Oncologists must continue to balance cancer risk and treatment-related toxicities.

Leptomeningeal Disease (LMD) in Patients with Melanoma Metastases

Leptomeningeal disease (LMD) is a devastating complication caused by seeding malignant cells to the cerebrospinal fluid (CSF) and the leptomeningeal membrane. LMD is diagnosed in 5-15% of patients with systemic malignancy. Management of LMD is challenging due to the biological and metabolic tumor microenvironment of LMD being largely unknown. Patients with LMD can present with a wide variety of signs and/or symptoms that could be multifocal and include headache, nausea, vomiting, diplopia, and weakness, among others. The median survival time for patients with LMD is measured in weeks and up to 3-6 months with aggressive management, and death usually occurs due to progressive neurologic dysfunction. In melanoma, LMD is associated with a suppressive immune microenvironment characterized by a high number of apoptotic and exhausted CD4⁺ T-cells, myeloid-derived suppressor cells, and a low number of CD8⁺ T-cells. Proteomics analysis revealed enrichment of complement cascade, which may disrupt the blood-CSF barrier. Clinical management of melanoma LMD consists primarily of radiation therapy, BRAF/MEK inhibitors as targeted therapy, and immunotherapy with anti-PD-1, anti-CTLA-4, and anti-LAG-3 immune checkpoint inhibitors. This review summarizes the biology and anatomic features of melanoma LMD, as well as the current therapeutic approaches.

Abstract OT3-19-01: Phase II Study of Screening Brain MRIs in Stage IV Breast Cancer

Background: As systemic therapy improves, there has been an increasing number of breast cancer patients who develop brain metastasis. Screening of asymptomatic stage IV breast cancer patients with brain MRIs is not currently recommended by the National Comprehensive Cancer Network (NCCN) Guidelines. Retrospective reports suggest breast cancer patients are more likely to present with more advanced central nervous system disease at the time of brain metastasis diagnosis compared to melanoma and non-small cell lung cancer (NSCLC) patients. This may be in part due to routine screening recommendations in melanoma and NSCLC. Early detection and treatment of brain metastases may improve outcomes for breast cancer patients. Trial Design: The study is designed as a single arm, nonrandomized phase II study, with the goal of investigating the role of screening brain MRIs in neurologically asymptomatic patients with metastatic breast cancer. Breast cancer patients will be allocated based on receptor subtypes into triple negative (TN), HER2+, and hormone receptor (HR)+/HER2- breast cancer. Following study enrollment, patients will undergo a screening brain MRI. Patients will undergo a second brain MRI at first systemic progression or at 6 months whichever event occurs sooner. Eligibility: Asymptomatic, stage IV breast cancer patients that have progressed past first line therapy in the metastatic setting with an ECOG/= 6 months are eligible. Specific Aims: The primary objective is to determine the incidence of asymptomatic brain metastasis in metastatic breast cancer by subtype. Secondary objectives include determining the incidence of asymptomatic leptomeningeal disease, the number and size of brain metastases at diagnosis, the number of patients requiring whole brain radiation therapy vs. stereotactic radiation following diagnosis and overall survival and brain metastasis specific survival following brain metastasis diagnosis in metastatic breast cancer by subtype. Statistical Methods: A total of 30, 30, and 40 TN, HER2+, and HR+/HER2-, breast cancer patients will be enrolled, respectively. Using an incidence rate of 17%, the 95% CI by subtype will be (0.06,0.351), (0.06,0.351), and (0.07,0.322). Patient Accrual: This study is open with 30 patients enrolled at the time of submission. A total of 100 patients will be enrolled. Contact Information: Kamran A. Ahmed MD, Moffitt Cancer Center, email: kamran.ahmed@moffitt.org, Clinical trial information: NCT05115474. Funding: Florida Breast Cancer Foundation.

Citation Format: Kamran A. Ahmed, Youngchul Kim, Avan Armaghani, John Arrington, Ricardo Costa, Brian J. Czerniecki, Roberto Diaz, Peter A. Forsyth, Hung Khong, Kimberley Lee, Loretta Loftus, Marilin Rosa, Hatem H. Soliman, Iman Washington, Aixa Soyano, Hyo S. Han. Phase II Study of Screening Brain MRIs in Stage IV Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT3-19-01.

Abstract PD7-06: Characteristics of Long-Term Survival in Breast Cancer Brain Metastasis after Stereotactic Radiation

Background: Advances in imaging and systemic therapy have improved the survival for patients with breast cancer brain metastases (BCBM). However, an improved understanding of patients with long-term survival after stereotactic radiation (SRT) for BCBM is warranted and could allow for better prognostication and personalized treatment. Methods: This is a single institution retrospective review of 188 patients who underwent SRT sessions to 685 BCBM from August 2004 to June 2020. Patients who were lost to follow up within 2 years after SRT were excluded. Patients were stratified into 2 groups: those with overall survival (OS) from SRT less than 2 years (short-term survival, STS) and those with OS from SRT of at least 2 years (long-term survival, LTS). Patient, tumor, and treatment characteristics were compared between the 2 groups via the student t-test and Chi-square testing as appropriate. The Kaplan-Meier (KM) method was used to calculate OS, local control (LC), and distant intracranial control (DIC) from the date of SRT. The reverse KM method was used to estimate follow-up from SRT. Results: The median follow up from BCBM diagnosis was 52.8 months (95% CI: 40.5-75.2 months). Of the 685 treated BCBMs, 552 (81%) received stereotactic radiosurgery (SRS) to a median dose of 21 Gy (12-24 Gy) and 133 received fractionated stereotactic radiation therapy (FSRT) to a median dose of 25 Gy (20-35 Gy) in 3-5 fractions. The 2-year LC, DIC, and OS was 78.4%, 26.5%, and 38.3%, respectively. The 5-year OS was 19%. There were 72 patients (38%) in the LTS group and 116 patients (62%) in the STS group. The LTS group had lower rates of invasive lobular carcinoma (0% vs 6%, p=0.001) and higher rate of HER2+ disease (61% vs 30%, p&lt; 0.001). The LTS group had lower rates of concurrent extracranial metastasis (74% vs 89%, p=0.008) and lung metastasis (33% vs 53%, p=0.009), though there were no differences in the rates of bone or liver metastasis. The LTS group had less BCBM at the time of SRT (mean 1.9 vs 2.5, p=0.013) and more often received SRT to a single BCBM (65% vs 42%, p=0.002). There were no significant differences in age or performance status between the groups. Conclusion: Prognosis for patients with BCBM is heterogeneous, as a minority of patients have prolonged OS after SRT. These patients more often have limited BCBM, HER2+ disease, and a lower extracranial disease burden.

Citation Format: Joseph D. Tang, Matthew N. Mills, Chetna Thawani, Daniel E. Oliver, Aixa Soyano, Arnold Etame, Hsiang-Hsuan Michael Yu, Nam Tran, Michael A. Vogelbaum, Peter A. Forsyth, Brian J. Czerniecki, Hatem H. Soliman, Hyo S. Han, Kamran A. Ahmed. Characteristics of Long-Term Survival in Breast Cancer Brain Metastasis after Stereotactic Radiation [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD7-06.

Improving Brain Metastases Outcomes Through Therapeutic Synergy Between Stereotactic Radiosurgery and Targeted Cancer Therapies

Brain metastases are the most common form of brain cancer. Increasing knowledge of primary tumor biology, actionable molecular targets and continued improvements in systemic and radiotherapy regimens have helped improve survival but necessitate multidisciplinary collaboration between neurosurgical, medical and radiation oncologists. In this review, we will discuss the advances of targeted therapies to date and discuss findings of studies investigating the synergy between these therapies and stereotactic radiosurgery for non-small cell lung cancer, breast cancer, melanoma, and renal cell carcinoma brain metastases.

A preclinical model of patient-derived cerebrospinal fluid circulating tumor cells for experimental therapeutics in leptomeningeal disease from melanoma

BACKGROUND

Leptomeningeal disease (LMD) occurs as a late complication of several human cancers and has no rationally designed treatment options. A major barrier to developing effective therapies for LMD is the lack of cell-based or preclinical models that recapitulate human disease. Here, we describe the development of in vitro and in vivo cultures of patient-derived cerebrospinal fluid circulating tumor cells (PD-CSF-CTCs) from patients with melanoma as a preclinical model to identify exploitable vulnerabilities in melanoma LMD.

METHODS

CSF-CTCs were collected from melanoma patients with melanoma-derived LMD and cultured ex vivo using human meningeal cell-conditioned media. Using immunoassays and RNA-sequencing analyses of PD-CSF-CTCs, molecular signaling pathways were examined and new therapeutic targets were tested for efficacy in PD-CSF-CTCs preclinical models.

RESULTS

PD-CSF-CTCs were successfully established both in vitro and in vivo. Global RNA analyses of PD-CSF-CTCs revealed several therapeutically tractable targets. These studies complimented our prior proteomic studies highlighting IGF1 signaling as a potential target in LMD. As a proof of concept, combining treatment of ceritinib and trametinib in vitro and in vivo demonstrated synergistic antitumor activity in PD-CSF-CTCs and BRAF inhibitor-resistant melanoma cells.

CONCLUSIONS

This study demonstrates that CSF-CTCs can be grown in vitro and in vivo from some melanoma patients with LMD and used as preclinical models. These models retained melanoma expression patterns and had signaling pathways that are therapeutically targetable. These novel models/reagents may be useful in developing rationally designed treatments for LMD.

Abstract OT2-09-01: Phase I/II study of stereotactic radiation and abemaciclib in the management of hormone receptor positive HER2 negative breast cancer brain metastases

Background: Breast cancer patients with brain metastases have a high unmet clinical need and improved management strategies are needed. There has been interest in studying CDK 4/6 inhibitors in the management of breast cancer brain metastases. A phase II study has shown abemaciclib to have activity in the management of hormone receptor (HR)+/HER2- brain metastases. Pre-clinical data suggests a potential synergy with CDK inhibitors and radiation therapy. Stereotactic radiosurgery (SRS) is a cornerstone in the management of limited brain metastases. We hypothesize treatment with abemaciclib and SRS will be safe and improve intracranial progression free survival (PFS) compared to abemaciclib alone. Trial Design: The study is designed as a prospective, single-arm, nonrandomized, open-label, phase I/II trial of abemaciclib and endocrine therapy with SRS among patients with HR+/HER2- metastatic breast cancer brain metastases. Treatment will be initiated with one week of abemaciclib followed by stereotactic radiation to sites of brain metastases or post-operative cavities with continued abemaciclib. Safety will be monitored initially by a 3+3 design. If unexpected neurologic toxicities are noted, the dose of radiation therapy will be reduced. This will be followed by a phase II study to evaluate intracranial PFS. Eligibility: Eligible patients include those that are HR+/HER2-, ≥18, ECOG ≤2 with ≤15 breast cancer brain metastases with measurable disease per Response Assessment in Neuro-Oncology Brain Metastases (RANO-BM) criteria. Specific Aims: The primary objective of the phase I study is to evaluate the safety and feasibility of abemaciclib and SRS to sites of brain metastases in the management of HR+/HER2- metastatic breast cancer with brain metastases. The primary objective of the phase II portion is to determine PFS intracranially. Secondary objectives include evaluation of extracranial PFS, local and distant intracranial control, and overall survival. Statistical Methods: Safety and feasibility will be monitored in the phase I study using a 3 + 3 design followed by a phase II study to assess intracranial PFS. The phase II study is designed as a single-arm, two-stage trial using the Restricted-Kwak-and-Jung’s method. In the first stage, a total of 21 patients will be enrolled. If pre-specified endpoints are met, an additional 10 patients will be enrolled in the second stage. Patient Accrual: A total of up to 31 patients will be enrolled inclusive of patients in the phase I portion treated at the recommended phase II dose. Clinical trial information: NCT04923542.

Citation Format: Kamran A. Ahmed, Youngchul Kim, Michelle DeJesus, Sasha J. Beyer, Nicole O. Williams, Joshua Palmer, Kristina D. Woodhouse, Rashmi K. Murthy, Jing Li, Avan J. Armaghani, John A. Arrington, Ricardo L. Costa, Brian J. Czerniecki, Arnold B. Etame, Peter A. Forsyth, Hung T. Khong, Daniel E. Oliver, Marilin Rosa, Solmaz Sahebjam, Hatem H. Soliman, Aixa E. Soyano, Michael A. Vogelbaum, Michael Yu, Hyo S. Han. Phase I/II study of stereotactic radiation and abemaciclib in the management of hormone receptor positive HER2 negative breast cancer brain metastases [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-09-01.

Identification of Immunogenic MHC Class II Human HER3 Peptides that Mediate Anti-HER3 CD4+ Th1 Responses and Potential Use as a Cancer Vaccine

The HER3/ERBB3 receptor is an oncogenic receptor tyrosine kinase that forms heterodimers with EGFR family members and is overexpressed in numerous cancers. HER3 overexpression associates with reduced survival and acquired resistance to targeted therapies, making it a potential therapeutic target in multiple cancer types. Here, we report on immunogenic, promiscuous MHC class II-binding HER3 peptides, which can generate HER3-specific CD4⁺ Th1 antitumor immune responses. Using an overlapping peptide screening methodology, we identified nine MHC class II-binding HER3 epitopes that elicited specific Th1 immune response in both healthy donors and breast cancer patients. Most of these peptides were not identified by current binding algorithms. Homology assessment of amino acid sequence BLAST showed >90% sequence similarity between human and murine HER3/ERBB3 peptide sequences. HER3 peptide-pulsed dendritic cell vaccination resulted in anti-HER3 CD4⁺ Th1 responses that prevented tumor development, significantly delayed tumor growth in prevention models, and caused regression in multiple therapeutic models of HER3-expressing murine tumors, including mammary carcinoma and melanoma. Tumors were robustly infiltrated with CD4⁺ T cells, suggesting their key role in tumor rejection. Our data demonstrate that class II HER3 promiscuous peptides are effective at inducing HER3-specific CD4⁺ Th1 responses and suggest their applicability in immunotherapies for human HER3-overexpressing tumors.

Long-term outcomes of patients with active melanoma brain metastases treated with combination nivolumab plus ipilimumab (CheckMate 204): final results of an open-label, multicentre, phase 2 study

BACKGROUND

Combination nivolumab plus ipilimumab was efficacious in patients with asymptomatic melanoma brain metastases (MBM) in CheckMate 204, but showed low efficacy in patients with symptomatic MBM. Here, we provide final 3-year follow-up data from the trial.

METHODS

This open-label, multicentre, phase 2 study (CheckMate 204) included adults (aged ≥18 years) with measurable MBM (0·5-3·0 cm in diameter). Asymptomatic patients (cohort A) had an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 and no neurological symptoms or baseline corticosteroid use; symptomatic patients (cohort B) had an ECOG performance status of 0-2 with stable neurological symptoms and could be receiving low-dose dexamethasone. Nivolumab 1 mg/kg plus ipilimumab 3 mg/kg was given intravenously every 3 weeks for four doses, followed by nivolumab 3 mg/kg every 2 weeks for up to 2 years, until disease progression or unacceptable toxicity. The primary endpoint was intracranial clinical benefit rate (complete responses, partial responses, or stable disease lasting ≥6 months) assessed in all treated patients. Intracranial progression-free survival and overall survival were key secondary endpoints. This study is registered with ClinicalTrials.gov, NCT02320058.

FINDINGS

Between Feb 19, 2015, and Nov 1, 2017, 119 (72%) of 165 screened patients were enrolled and treated: 101 patients were asymptomatic (cohort A; median follow-up 34·3 months [IQR 14·7-36·4]) and 18 were symptomatic (cohort B; median follow-up 7·5 months [1·2-35·2]). Investigator-assessed intracranial clinical benefit was observed in 58 (57·4% [95% CI 47·2-67·2]) of 101 patients in cohort A and three (16·7% [3·6-41·4]) of 18 patients in cohort B; investigator-assessed objective response was observed in 54 (53·5% [43·3-63·5]) patients in cohort A and three (16·7% [3·6-41·4]) patients in cohort B. 33 (33%) patients in cohort A and three (17%) patients in cohort B had an investigator-assessed intracranial complete response. For patients in cohort A, 36-month intracranial progression-free survival was 54·1% (95% CI 42·7-64·1) and overall survival was 71·9% (61·8-79·8). For patients in cohort B, 36-month intracranial progression-free survival was 18·9% (95% CI 4·6-40·5) and overall survival was 36·6% (14·0-59·8). The most common grade 3-4 treatment-related adverse events (TRAEs) were increased alanine aminotransferase and aspartate aminotransferase (15 [15%] of 101 patients each) in cohort A; no grade 3 TRAEs occurred in more than one patient each in cohort B, and no grade 4 events occurred. The most common serious TRAEs were colitis, diarrhoea, hypophysitis, and increased alanine aminotransferase (five [5%] of each among the 101 patients in cohort A); no serious TRAE occurred in more than one patient each in cohort B. There was one treatment-related death (myocarditis in cohort A).

INTERPRETATION

The durable 3-year response, overall survival, and progression-free survival rates for asymptomatic patients support first-line use of nivolumab plus ipilimumab. Symptomatic disease in patients with MBM remains difficult to treat, but some patients achieve a long-term response with the combination.

FUNDING

Bristol Myers Squibb.

Nivolumab and Stereotactic Radiosurgery for Patients With Breast Cancer Brain Metastases: A Nonrandomized, Open-Label Phase 1b Study

Purpose

Methods and Materials

Results

Conclusions

The presentation of brain metastases in melanoma, non-small cell lung cancer, and breast cancer and potential implications for screening brain MRIs

PURPOSE

This study assessed the presentation and institutional outcomes treating brain metastases (BM) of breast cancer (BC), non-small cell lung cancer (NSCLC), and melanoma origin.

METHODS

Patients with brain metastases treated between 2014 and 2019 with primary melanoma, NSCLC, and BC were identified. Overall survival (OS) was calculated from dates of initial BM diagnosis using the Kaplan-Meier method.

RESULTS

A total of 959 patients were identified including melanoma (31%), NSCLC (51%), and BC (18%). Patients with BC were younger at BM diagnosis (median age: 57) than NSCLC (65) and melanoma patients (62, p < 0.0001). Breast cancer patients were more likely to present with at least 5 BM (27%) than NSCLC (14%) and melanoma (13%), leptomeningeal disease (23%, 6%, and 6%, p = 0.0004) and receive whole brain radiation therapy (WBRT) (58%, 37%, and 22%, p < 0.0001). There were no differences in surgical resection (24%, 24%, and 29%, p = 0.166). Median OS was shorter for BC patients (9.9, 10.3, and 13.7 months, p = 0.0006).

CONCLUSION

Breast cancer patients were more likely to be younger, present with advanced disease, require WBRT, and have poorer OS than NSCLC and melanoma patients. Further investigation is needed to determine which BC patients are at sufficient risk for brain MRI screening.

Single-Cell Characterization of the Immune Microenvironment of Melanoma Brain and Leptomeningeal Metastases

PURPOSE

Melanoma brain metastases (MBM) and leptomeningeal melanoma metastases (LMM) are two different manifestations of melanoma CNS metastasis. Here, we used single-cell RNA sequencing (scRNA-seq) to define the immune landscape of MBM, LMM, and melanoma skin metastases.

EXPERIMENTAL DESIGN

scRNA-seq was undertaken on 43 patient specimens, including 8 skin metastases, 14 MBM, and 19 serial LMM specimens. Detailed cell type curation was performed, the immune landscapes were mapped, and key results were validated by IHC and flow cytometry. Association analyses were undertaken to identify immune cell subsets correlated with overall survival.

RESULTS

The LMM microenvironment was characterized by an immune-suppressed T-cell landscape distinct from that of brain and skin metastases. An LMM patient with long-term survival demonstrated an immune repertoire distinct from that of poor survivors and more similar to normal cerebrospinal fluid (CSF). Upon response to PD-1 therapy, this extreme responder showed increased levels of T cells and dendritic cells in their CSF, whereas poor survivors showed little improvement in their T-cell responses. In MBM patients, therapy led to increased immune infiltrate, with similar T-cell transcriptional diversity noted between skin metastases and MBM. A correlation analysis across the entire immune landscape identified the presence of a rare population of dendritic cells (DC3) that was associated with increased overall survival and positively regulated the immune environment through modulation of activated T cells and MHC expression.

CONCLUSIONS

Our study provides the first atlas of two distinct sites of melanoma CNS metastases and defines the immune cell landscape that underlies the biology of this devastating disease.

Hypofractionated stereotactic re-irradiation with pembrolizumab and bevacizumab in patients with recurrent high-grade gliomas: results from a phase I study

BACKGROUND

Radiotherapy may synergize with programmed cell death 1 (PD1)/PD1 ligand (PD-L1) blockade. The purpose of this study was to determine the recommended phase II dose, safety/tolerability, and preliminary efficacy of combining pembrolizumab, an anti-PD1 monoclonal antibody, with hypofractionated stereotactic irradiation (HFSRT) and bevacizumab in patients with recurrent high-grade gliomas (HGGs).

METHODS

Eligible subjects with recurrent glioblastoma or anaplastic astrocytoma were treated with pembrolizumab (100 or 200 mg based on dose level Q3W) concurrently with HFSRT (30 Gy in 5 fractions) and bevacizumab 10 mg/kg Q2W.

RESULTS

Thirty-two patients were enrolled (bevacizumab-naïve, n = 24; bevacizumab-resistant, n = 8). The most common treatment-related adverse events (TRAEs) were proteinuria (40.6%), fatigue (25%), increased alanine aminotransferase (25%), and hypertension (25%). TRAEs leading to discontinuation occurred in 1 patient who experienced a grade 3 elevation of aspartate aminotransferase. In the bevacizumab-naïve cohort, 20 patients (83%) had a complete response or partial response. The median overall survival (OS) and progression-free survival (PFS) were 13.45 months (95% CI: 9.46-18.46) and 7.92 months (95% CI: 6.31-12.45), respectively. In the bevacizumab-resistant cohort, PR was achieved in 5 patients (62%). Median OS was 9.3 months (95% CI: 8.97-18.86) with a median PFS of 6.54 months (95% CI: 5.95-18.86). The majority of patients (n = 20/26; 77%) had tumor-cell/tumor-microenvironment PD-L1 expression <1%.

CONCLUSIONS

The combination of HFSRT with pembrolizumab and bevacizumab in patients with recurrent HGG is generally safe and well tolerated. These findings merit further investigation of HFSRT with immunotherapy in HGGs.

Capecitabine and stereotactic radiation in the management of breast cancer brain metastases

Background

Little is known about the safety and efficacy of concurrent capecitabine and stereotactic radiotherapy in the setting of breast cancer brain metastases (BCBM).

Methods

Twenty-three patients with BCBM underwent 31 stereotactic sessions to 90 lesions from 2005 to 2019 with receipt of capecitabine. The Kaplan-Meier method was used to calculate overall survival (OS), local control (LC), and distant intracranial control (DIC) from the date of stereotactic radiation. Imaging was independently reviewed by a neuro-radiologist.

Results

Median follow-up from stereotactic radiation was 9.2 months. Receptor types of patients treated included triple negative (n = 7), hormone receptor (HR)+/HER2- (n = 7), HR+/HER2+ (n = 6), and HR−/HER2+ (n = 3). Fourteen patients had stage IV disease prior to BCBM diagnosis. The median number of brain metastases treated per patient was 3 (1 to 12). The median dose of stereotactic radiosurgery (SRS) was 21 Gy (range: 15–24 Gy) treated in a single fraction and for lesions treated with fractionated stereotactic radiation therapy (FSRT) 25 Gy (24–30 Gy) in a median of 5 fractions (range: 3–5). Of the 31 stereotactic sessions, 71% occurred within 1 month of capecitabine. No increased toxicity was noted in our series with no cases of radionecrosis. The 1-year OS, LC, and DIC were 46, 88, and 30%, respectively.

Conclusions

In our single institution experience, we demonstrate stereotactic radiation and capecitabine to be a safe treatment for patients with BCBM with adequate LC. Further study is needed to determine the potential synergy between stereotactic radiation and capecitabine in the management of BCBM.

Safety and Efficacy of the Combination of Nivolumab Plus Ipilimumab in Patients With Melanoma and Asymptomatic or Symptomatic Brain Metastases (CheckMate 204)

Background

In patients with melanoma and asymptomatic brain metastases (MBM), nivolumab plus ipilimumab provided an intracranial response rate of 55%. Here, we present the first report for patients who were symptomatic and/or required corticosteroids and updated data for asymptomatic patients.

Methods

Patients with measurable MBM, 0.5-3.0 cm, were enrolled into Cohort A (asymptomatic) or Cohort B (stable neurologic symptoms and/or receiving corticosteroids). Nivolumab, 1 mg/kg, and ipilimumab, 3 mg/kg, were given intravenously every 3 weeks ×4, followed by nivolumab, 3 mg/kg, every 2 weeks until progression, unacceptable toxicity, or 24 months. The primary endpoint was intracranial clinical benefit rate (CBR; complete response [CR], partial response [PR], or stable disease ≥6 months).

Results

Symptomatic patients (N = 18) received a median of one nivolumab and ipilimumab combination dose and had an intracranial CBR of 22.2%. Two of 12 patients on corticosteroids had CR; 2 responded among the 6 not on corticosteroids. Median intracranial progression-free survival (PFS) and overall survival (OS) were 1.2 and 8.7 months, respectively. In contrast, with 20.6 months of follow-up, we confirmed an intracranial CBR of 58.4% in asymptomatic patients (N = 101); median duration of response, PFS, and OS were not reached. No new safety signals were observed.

Conclusions

Nivolumab plus ipilimumab provides durable clinical benefit for asymptomatic patients with MBM and should be considered for first-line therapy. This regimen has limited activity in MBM patients with neurologic symptoms and/or requiring corticosteroids, supporting the need for alternative approaches and methods to reduce the dependency on corticosteroids.

Clinical trial registration. ClinicalTrials.gov, NCT02320058.

Trastuzumab Emtansine (T-DM1) and stereotactic radiation in the management of HER2+ breast cancer brain metastases

Background

Due to recent concerns about the toxicity of trastuzumab emtansine (T-DM1) with stereotactic radiation, we assessed our institutional outcomes treating HER2-positive breast cancer brain metastases (BCBM) with T-DM1 and stereotactic radiation.

Methods

This is a single institution series of 16 patients with HER2-positive breast cancer who underwent 18 stereotactic sessions to 40 BCBM from 2013 to 2019 with T-DM1 delivered within 6 months. The Kaplan-Meier method was used to calculate overall survival (OS), local control (LC), distant intracranial control (DIC), and systemic progression-free survival (sPFS) from the date of SRS. A neuro-radiologist independently reviewed follow-up imaging.

Results

One patient had invasive lobular carcinoma, and 15 patients had invasive ductal carcinoma. All cases were HER2-positive, while 10 were hormone receptor (HR) positive. Twenty-four lesions were treated with stereotactic radiosurgery (SRS) to a median dose of 21 Gy (14–24 Gy). Sixteen lesions were treated with fractionated stereotactic radiation (FSRT) with a median dose of 25 Gy (20-30Gy) delivered in 3 to 5 fractions. Stereotactic radiation was delivered concurrently with T-DM1 in 19 lesions (48%). Median follow up time was 13.2 months from stereotactic radiation. The 1-year LC, DIC, sPFS, and OS were 75, 50, 30, and 67%, respectively. There was 1 case of leptomeningeal progression and 1 case (3%) of symptomatic radionecrosis.

Conclusions

We demonstrate that stereotactic radiation and T-DM1 is well-tolerated and effective for patients with HER2-positive BCBM. An increased risk for symptomatic radiation necrosis was not noted in our series.

Targeted Therapy Given after Anti-PD-1 Leads to Prolonged Responses in Mouse Melanoma Models through Sustained Antitumor Immunity

Immunotherapy (IT) and targeted therapy (TT) are both effective against melanoma, but their combination is frequently toxic. Here, we investigated whether the sequence of IT (anti-PD-1)→ TT (ceritinib-trametinib or dabrafenib-trametinib) was associated with improved antitumor responses in mouse models of BRAF- and NRAS-mutant melanoma. Mice with NRAS-mutant (SW1) or BRAF-mutant (SM1) mouse melanomas were treated with either IT, TT, or the sequence of IT→TT. Tumor volumes were measured, and samples from the NRAS-mutant melanomas were collected for immune-cell analysis, single-cell RNA sequencing (scRNA-seq), and reverse phase protein analysis (RPPA). scRNA-seq demonstrated that the IT→TT sequence modulated the immune environment, leading to increased infiltration of T cells, monocytes, dendritic cells and natural killer cells, and decreased numbers of tumor-associated macrophages, myeloid-derived suppressor cells, and regulatory T cells. Durable responses to the IT→TT sequence were dependent on T-cell activity, with depletion of CD8⁺, but not CD4⁺, T cells abrogating the therapeutic response. An analysis of transcriptional heterogeneity in the melanoma compartment showed the sequence of IT→TT enriched for a population of melanoma cells with increased expression of MHC class I and melanoma antigens. RPPA analysis demonstrated that the sustained immune response induced by IT→TT suppressed tumor-intrinsic signaling pathways required for therapeutic escape. These studies establish that upfront IT improves the responses to TT in BRAF- and NRAS-mutant melanoma models.

Abstract PS14-19: Characteristics of breast cancer brain metastases presentation by subtype and validation of the modified breast graded prognostic assessment

Purpose: Breast cancer brain metastases (BCBM) diagnosis is increasing in frequency due to improved systemic control and imaging techniques. Differences have been noted in rates of central nervous system (CNS) relapse and biologic subtype. The modified breast graded prognostic assessment (breast-GPA) was initially validated in patients treated between 1996-2013 and considers biologic subtype. In this study, we characterize patients diagnosed with BCBM by subtype and validate the breast-GPA in a modern cohort of patients.

Methods: All patients with BCBM treated at our institution with radiotherapy between 2016 and 2019 were identified. Characteristics of patients’ initial brain metastasis diagnosis were retrieved from the clinical chart and radiologic examinations. To test differences between cohorts, the Kruskal-Wallis and Pearson’s chi-square tests were used when appropriate. Overall survival (OS) was calculated from the date of brain metastasis diagnosis to the date of death using the Kaplan-Meier (KM) method, with the log-rank test used to examine differences between groups.

Results: A total of 122 BCBM patients were identified. Breast cancer subtypes included hormone receptor (HR)+/HER2- (45%), triple negative (TN) (25%), HR-/HER2+ (16%), and HR+/HER2+ (14%). The first treatment for BCBM patients following diagnosis was whole brain radiation (51%), surgery followed by stereotactic radiation (28%), and stereotactic radiation (21%). The interval between breast cancer diagnosis and diagnosis of BCBM was longest for HR+/HER2- 4.5 years, followed by TN 2.8 years, HR+/HER2+ 2.3 years, HR-/HER2+ 1.9 years, p=0.003. The interval from systemic metastases to BCBM diagnosis trended towards the shortest for TN patients 6.6 months, p=0.15. A total of 34 patients (28%) were diagnosed with leptomeningeal disease (LMD) at initial brain metastases presentation. LMD was diagnosed most commonly at presentation in HR+/HER2- (36%) followed by , TN (26%), HR-/HER2+ (26%), and HR+/HER2+ (6%), p=0.06. No differences were noted based on receptor typessubtype and age, symptomatic intracranial disease, number of brain metastases, type of first intracranial treatment or concurrent systemic metastases at initial BCBM presentation, all p &gt; 0.05. Twenty-four month KM OS rates following diagnosis of brain metastasis for breast-GPA 0-1, 1.5-2, 2.5-3, and 3.5-4 groups were 14%, 27%, 33%, and 86% (p=0.0005), respectively.

Conclusions: In our institutional analysis, similarities were noted in the initial presentation of BCBM based on receptor typesubtype. Significant differences were noted in OS based on the modified breast-GPA. Further investigation is needed to determine which subtypes of asymptomatic breast cancer patients are at sufficient risk to warrant brain MRI screening.

Citation Format: Yuki Kawahara, Matthew Fahey, Thrisha K Potluri, Matthew N Mills, Nicholas B Figura, Iman R Washington, Roberto Diaz, Timothy J Robinson, Hsiang-Hsuan M Yu, Arnold B Etame, James Liu, Michael A Vogelbaum, Brian J Czerniecki, Peter A Forsyth, Hatem H Soliman, Hyo S Han, Kamran A Ahmed. Characteristics of breast cancer brain metastases presentation by subtype and validation of the modified breast graded prognostic assessment [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS14-19.

A Murine Ommaya Xenograft Model to Study Direct-Targeted Therapy of Leptomeningeal Disease

Leptomeningeal disease (LMD) is an uncommon type of central nervous system (CNS) metastasis to the cerebral spinal fluid (CSF). The most common cancers that cause LMD are breast and lung cancers and melanoma. Patients diagnosed with LMD have a very poor prognosis and generally survive for only a few weeks or months. One possible reason for the lack of efficacy of systemic therapy against LMD is the failure to achieve therapeutically effective concentrations of drug in the CSF because of an intact and relatively impermeable blood-brain barrier (BBB) or blood-CSF barrier across the choroid plexus. Therefore, directly administering drugs intrathecally or intraventricularly may overcome these barriers. This group has developed a model that allows for the effective delivery of therapeutics (i.e., drugs, antibodies, and cellular therapies) chronically and the repeated sampling of CSF to determine drug concentrations and target modulation in the CSF (when the tumor microenvironment is targeted in mice). The model is the murine equivalent of a magnetic resonance imaging-compatible Ommaya reservoir, which is used clinically. This model, which is affixed to the skull, has been designated as the "Murine Ommaya." As a therapeutic proof of concept, human epidermal growth factor receptor 2 antibodies (clone 7.16.4) were delivered into the CSF via the Murine Ommaya to treat mice with LMD from human epidermal growth factor receptor 2-positive breast cancer. The Murine Ommaya increases the efficiency of drug delivery using a miniature access port and prevents the wastage of excess drug; it does not interfere with CSF sampling for molecular and immunological studies. The Murine Ommaya is useful for testing novel therapeutics in experimental models of LMD.

Durable Progression-Free Survival With the Use of BRAF and MEK Inhibitors in Four Cases With BRAF V600E-Mutated Gliomas

INTRODUCTION

BRAF V600 E mutations have been identified in a subset of patients with primary brain tumors. Combination therapy with BRAF and Mitogen-activated protein kinase (MEK) inhibitors (BRAF/MEKi) targeting sequential steps in the MAPK pathway has replaced BRAFi monotherapy as the standard of care in multiple tumors with BRAF V600 E mutations, and clinical evidence for this strategy continues to grow in primary brain tumors.

CASE SERIES

We describe four patients with BRAF V600 E mutated gliomas, including a 21-year-old woman with a ganglioglioma WHO grade I, a 19-year-old man with a pleomorphic xanthoastrocytoma WHO grade III, and 21-year-old and 33-year-old women with epithelioid GBM WHO grade IV, who achieved durable progression-free survival with combination BRAF/MEKi.

CONCLUSION

Combination of BRAF/MEK inhibition can be a novel, promising approach as targeted therapy in gliomas with BRAF V600 E mutations, especially those that are resistant to standard therapy. Our cases, along with other early reports utilizing dabrafenib/trametinib, highlight the importance of somatic next-generation sequencing, particularly in younger patients. Interim results from clinical trials utilizing dabrafenib/trametinib have been promising thus far, and our case series suggests that durable clinical benefit is possible, even in the setting of glioblastoma, WHO grade IV.

Noncanonical EphA2 Signaling Is a Driver of Tumor-Endothelial Cell Interactions and Metastatic Dissemination in BRAF Inhibitor‒Resistant Melanoma

Acquired BRAF/MAPK/extracellular signal‒regulated kinase inhibitor resistance in melanoma results in a new transcriptional state associated with an increased risk of metastasis. In this study, we identified noncanonical ephrin receptor (Eph) EphA2 signaling as a driver of the resistance-associated metastatic state. We used mass spectrometry‒based proteomic and phenotypic assays to demonstrate that the expression of active noncanonical EphA2-S897E in melanoma cells led to a mesenchymal-to-amoeboid transition driven by Cdc42 activation. The induction of mesenchymal-to-amoeboid transition promoted melanoma cell invasion, survival under shear stress, adhesion to endothelial cells under continuous-flow conditions, increased permeability of endothelial cell monolayers, and stimulated melanoma transendothelial cell migration. In vivo, melanoma cells expressing EphA2-S897E or active Cdc42 showed superior lung retention after tail-vain injection. Analysis of BRAF inhibitor‒sensitive and ‒resistant melanoma cells demonstrated resistance to be associated with a mesenchymal-to-amoeboid transition switch, upregulation of Cdc42 activity, increased invasion, and transendothelial migration. The drug-resistant metastatic state was dependent on histone deacetylase 8 activity. Silencing of histone deacetylase 8 led to the inhibition of EphA2 and protein kinase B phosphorylation, reduced invasion, and impaired melanoma cell-endothelial cell interactions. In summary, we have demonstrated that the metastatic state associated with acquired BRAF inhibitor resistance is dependent on noncanonical EphA2 signaling, leading to increased melanoma-endothelial cell interactions and enhanced tumor dissemination.

Tumor Volume Dynamics as an Early Biomarker for Patient-Specific Evolution of Resistance and Progression in Recurrent High-Grade Glioma

Recurrent high-grade glioma (HGG) remains incurable with inevitable evolution of resistance and high inter-patient heterogeneity in time to progression (TTP). Here, we evaluate if early tumor volume response dynamics can calibrate a mathematical model to predict patient-specific resistance to develop opportunities for treatment adaptation for patients with a high risk of progression. A total of 95 T1-weighted contrast-enhanced (T1post) MRIs from 14 patients treated in a phase I clinical trial with hypo-fractionated stereotactic radiation (HFSRT; 6 Gy × 5) plus pembrolizumab (100 or 200 mg, every 3 weeks) and bevacizumab (10 mg/kg, every 2 weeks; NCT02313272) were delineated to derive longitudinal tumor volumes. We developed, calibrated, and validated a mathematical model that simulates and forecasts tumor volume dynamics with rate of resistance evolution as the single patient-specific parameter. Model prediction performance is evaluated based on how early progression is predicted and the number of false-negative predictions. The model with one patient-specific parameter describing the rate of evolution of resistance to therapy fits untrained data ( R 2 = 0.70 ). In a leave-one-out study, for the nine patients that had T1post tumor volumes ≥1 cm3, the model was able to predict progression on average two imaging cycles early, with a median of 9.3 (range: 3-39.3) weeks early (median progression-free survival was 27.4 weeks). Our results demonstrate that early tumor volume dynamics measured on T1post MRI has the potential to predict progression following the protocol therapy in select patients with recurrent HGG. Future work will include testing on an independent patient dataset and evaluation of the developed framework on T2/FLAIR-derived data.

Proteomic Analysis of CSF from Patients with Leptomeningeal Melanoma Metastases Identifies Signatures Associated with Disease Progression and Therapeutic Resistance

PURPOSE

The development of leptomeningeal melanoma metastases (LMM) is a rare and devastating complication of the late-stage disease, for which no effective treatments exist. Here, we performed a multi-omics analysis of the cerebrospinal fluid (CSF) from patients with LMM to determine how the leptomeningeal microenvironment shapes the biology and therapeutic responses of melanoma cells.

EXPERIMENTAL DESIGN

A total of 45 serial CSF samples were collected from 16 patients, 8 of these with confirmed LMM. Of those with LMM, 7 had poor survival (<4 months) and one was an extraordinary responder (still alive with survival >35 months). CSF samples were analyzed by mass spectrometry and incubated with melanoma cells that were subjected to RNA sequencing (RNA-seq) analysis. Functional assays were performed to validate the pathways identified.

RESULTS

Mass spectrometry analyses showed the CSF of most patients with LMM to be enriched for pathways involved in innate immunity, protease-mediated damage, and IGF-related signaling. All of these were anticorrelated in the extraordinary responder. RNA-seq analysis showed CSF to induce PI3K/AKT, integrin, B-cell activation, S-phase entry, TNFR2, TGFβ, and oxidative stress responses in the melanoma cells. ELISA assays confirmed that TGFβ expression increased in the CSF of patients progressing with LMM. CSF from poorly responding patients conferred tolerance to BRAF inhibitor therapy in apoptosis assays.

CONCLUSIONS

These analyses identified proteomic/transcriptional signatures in the CSF of patients who succumbed to LMM. We further showed that the CSF from patients with LMM has the potential to modulate BRAF inhibitor responses and may contribute to drug resistance.See related commentary by Glitza Oliva and Tawbi, p. 2083.

Abstract OT3-10-01: Phase Ib study of stereotactic radiation and nivolumab in the management of metastatic breast cancer with brain metastases

Background:Patients with breast cancer brain metastases represent a poor prognosis cohort with a high unmet clinical need. Standard-of-care treatments for patients with breast cancer brain metastases include local treatments, such as surgical resection and radiation treatment modalities that include stereotactic radiosurgery (SRS) or whole brain radiotherapy. Numerous pre-clinical studies have provided evidence to combine radiation therapy with immune checkpoint inhibition to improve response rates. The evidence is strongest for short course, hypofractionated radiation regimens. We hypothesize treatment with nivolumab and SRS will be feasible and well tolerated and may improve intracranial tumor control rates compared to SRS alone. Trial Design:The study is designed as a prospective, single-arm, nonrandomized, open-label, phase Ib trial of nivolumab and SRS among patients with metastatic breast cancer brain metastases. Treatment will be initiated with a dose of nivolumab (480 mg IV) that will be repeated every 4 weeks. The initial dose of nivolumab will be followed 1 week later by SRS at sites of brain metastases or post-operative cavities. Patients will be allowed to continue endocrine and HER2-targeted therapies if brain metastases progression was noted on these agents.Eligibility:Eligible patients include those ≥18, ECOG ≤2 with ≤10 breast cancer brain metastases of all subtypes eligible for stereotactic radiation. Specific Aims:The primary objective is to evaluate the safety and feasibility of nivolumab and SRS to sites of brain metastases. Secondary objectives include evaluation of intracranial progression free survival (PFS), extracranial PFS, overall survival, local control, and distant brain control. Correlative aims include assessing blood and tissue biomarkers (i.e. PD-L1, mutation burden, TCR repertoire etc.) for association with clinical benefit.Statistical Methods:Safety and feasibility will be monitored by a 3 + 3 design followed by a dose expansion phase. Patient Accrual:This study is open with 4 patients enrolled at the time of submission. A total of 12 patients will be enrolled.Contact Information:Kamran A. Ahmed MD, Moffitt Cancer Center, email: kamran.ahmed@moffitt.org, Clinical trial information: NCT03807765.

Citation Format: Kamran A Ahmed, Youngchul Kim, Avan J. Armaghani, John A. Arrington, Jimmy J. Caudell, Ricardo L. Costa, Brian J. Czerniecki, Arnold B. Etame, Peter A. Forsyth, Hung T. Khong, Sungjune Kim, Loretta Loftus, Timothy J. Robinson, Marilin Rosa, Solmaz Sahebjam, Hatem H. Soliman, Aixa E. Soyano, Nam D. Tran, H. Michael Yu, Hyo S. Han. Phase Ib study of stereotactic radiation and nivolumab in the management of metastatic breast cancer with brain metastases [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr OT3-10-01.

Management of brain metastases in breast cancer: a review of current practices and emerging treatments

PURPOSE

Breast cancer brain metastases (BCBM) are becoming an increasingly common diagnosis due to improved systemic control and more routine surveillance imaging. Treatment continues to require a multidisciplinary approach managing systemic and intracranial disease burden. Although, improvements have been made in the diagnosis and management of BCBM, brain metastasis patients continue to pose a challenge for practitioners.

METHODS

In this review, a group of medical oncologists, radiation oncologists, radiologists, breast surgeons, and neurosurgeons specializing in the treatment of breast cancer reviewed the available published literature and compiled a comprehensive review on the current state of BCBM.

RESULTS

We discuss the pathogenesis, epidemiology, diagnosis, treatment options (including systemic, surgical, and radiotherapy treatment modalities), and treatment response evaluation for BCBM. Furthermore, we discuss the ongoing prospective trials enrolling BCBM patients and their biologic rationale.

CONCLUSIONS

BCBM management is an increasing clinical concern. Multidisciplinary management combining the strengths of surgical, systemic, and radiation treatment modalities with prospective trials incorporating knowledge from the basic and translational sciences will ultimately lead to improved clinical outcomes for BCBM patients.

Breast leptomeningeal disease: a review of current practices and updates on management

PURPOSE

Leptomeningeal disease (LMD) is an advanced metastatic disease presentation portending a poor prognosis with minimal treatment options. The advent and widespread use of new systemic therapies for metastatic breast cancer has improved systemic disease control and extended survival; however, as patients live longer, the rates of breast cancer LMD are increasing.

METHODS

In this review, a group of medical oncologists, radiation oncologists, radiologists, breast surgeons, and neurosurgeons specializing in treatment of breast cancer reviewed the available published literature and compiled a comprehensive review on the current state of breast cancer LMD.

RESULTS

We discuss the pathogenesis, epidemiology, diagnosis, treatment options (including systemic, intrathecal, surgical, and radiotherapy treatment modalities), and treatment response evaluation specific to breast cancer patients. Furthermore, we discuss the controversies within this unique clinical setting and identify potential clinical opportunities to improve upon the diagnosis, treatment, and treatment response evaluation in the management of breast LMD.

CONCLUSIONS

We recognize the shortcomings in our current understanding of the disease and explore the future role of genomic/molecular disease characterization, technological innovations, and ongoing clinical trials attempting to improve the prognosis for this advanced disease state.

Melanoma central nervous system metastases: An update to approaches, challenges, and opportunities

In February 2018, the Melanoma Research Foundation and the Moffitt Cancer Center hosted the Second Summit on Melanoma Central Nervous System (CNS) Metastases in Tampa, Florida. In this white paper, we outline the current status of basic science, translational, and clinical research into melanoma brain metastasis development and therapeutic management. We further outline the important challenges that remain for the field and the critical barriers that need to be overcome for continued progress to be made in this clinically difficult area.

Combined Nivolumab and Ipilimumab in Melanoma Metastatic to the Brain

BACKGROUND

Brain metastases are a common cause of disabling neurologic complications and death in patients with metastatic melanoma. Previous studies of nivolumab combined with ipilimumab in metastatic melanoma have excluded patients with untreated brain metastases. We evaluated the efficacy and safety of nivolumab plus ipilimumab in patients with melanoma who had untreated brain metastases.

METHODS

In this open-label, multicenter, phase 2 study, patients with metastatic melanoma and at least one measurable, nonirradiated brain metastasis (tumor diameter, 0.5 to 3 cm) and no neurologic symptoms received nivolumab (1 mg per kilogram of body weight) plus ipilimumab (3 mg per kilogram) every 3 weeks for up to four doses, followed by nivolumab (3 mg per kilogram) every 2 weeks until progression or unacceptable toxic effects. The primary end point was the rate of intracranial clinical benefit, defined as the percentage of patients who had stable disease for at least 6 months, complete response, or partial response.

RESULTS

Among 94 patients with a median follow-up of 14.0 months, the rate of intracranial clinical benefit was 57% (95% confidence interval [CI], 47 to 68); the rate of complete response was 26%, the rate of partial response was 30%, and the rate of stable disease for at least 6 months was 2%. The rate of extracranial clinical benefit was 56% (95% CI, 46 to 67). Treatment-related grade 3 or 4 adverse events were reported in 55% of patients, including events involving the central nervous system in 7%. One patient died from immune-related myocarditis. The safety profile of the regimen was similar to that reported in patients with melanoma who do not have brain metastases.

CONCLUSIONS

Nivolumab combined with ipilimumab had clinically meaningful intracranial efficacy, concordant with extracranial activity, in patients with melanoma who had untreated brain metastases. (Funded by Bristol-Myers Squibb and the National Cancer Institute; CheckMate 204 ClinicalTrials.gov number, NCT02320058 .).

Experimental Treatments for Leptomeningeal Metastases From Solid Malignancies

BACKGROUND

Leptomeningeal metastasis is a consequence of advanced solid malignancies and has limited treatment options. It is possible that it is becoming more common as the leptomeninges act as a sanctuary site for recurrence from systemic cancer.

METHODS

Potential targeted and immunotherapy agents for the most common types of solid-tumor leptomeningeal metastasis are reviewed, as are their dosing/delivery strategies and novel, immunological approaches.

RESULTS

Historically, patients with leptomeningeal metastasis have been excluded from clinical trials, and data on the management of leptomeningeal metastasis come from single case reports and retrospective analyses.

CONCLUSION

For the first time ever, published reports suggest the tide may be turning in this challenging disease.

Clinical outcomes of melanoma brain metastases treated with stereotactic radiosurgery and anti-PD-1 therapy, anti-CTLA-4 therapy, BRAF/MEK inhibitors, BRAF inhibitor, or conventional chemotherapy

BACKGROUND

The effect of immunologic and targeted agents on intracranial response rates in patients with melanoma brain metastases (MBMs) is not yet clearly understood. This report analyzes outcomes of intact MBMs treated with single-session stereotactic radiosurgery (SRS) and anti-PD-1 therapy, anti-CTLA-4 therapy, BRAF/MEK inhibitors(i), BRAFi, or conventional chemotherapy.

PATIENTS AND METHODS

Patients were included if MBMs were treated with single-session SRS within 3 months of receiving systemic therapy. The primary end point of this study was distant MBM control. Secondary end points were local MBM control defined as a >20% volume increase on follow-up MRI, systemic progression-free survival, overall survival (OS) from both SRS and cranial metastases diagnosis, and neurotoxicity. Images were reviewed alongside two neuro-radiologists at our institution.

RESULTS

Ninety-six patients were treated to 314 MBMs over 119 SRS treatment sessions between January 2007 and August 2015. No significant differences were noted in age (P = 0.27), gender (P = 0.85), treated gross tumor volume (P = 0.26), or the diagnosis-specific graded prognostic assessment (P = 0.51) between the treatment cohorts. Twelve-month Kaplan-Meier (KM) distant MBM control rates were 38%, 21%, 20%, 8%, and 5% (P = 0.008) for SRS with anti-PD-1 therapies, anti-CTLA-4 therapy, BRAF/MEKi, BRAFi, and conventional chemotherapy, respectively. No significant differences were noted in the KM local MBM control rates among treatment groups (P = 0.25). Treatment with anti-PD-1 therapy, anti-CTLA-4 therapy, or BRAF/MEKi significantly improved OS on both univariate and multivariate analyses when compared with conventional chemotherapy.

CONCLUSION

In our institutional analysis of patients treated with SRS and various systemic immunologic and targeted melanoma agents, significant differences in distant MBM control and OS are noted. Prospective evaluation of the potential synergistic effect between these agents and SRS is warranted.

Managing leptomeningeal melanoma metastases in the era of immune and targeted therapy

Melanoma frequently metastasizes to the brain, with CNS involvement being clinically evident in ∼30% of patients (as high as 75% at autopsy). In ∼5% cases melanoma cells also metastasize to the leptomeninges, the sub-arachnoid space and cerebrospinal fluid (CSF). Patients with leptomeningeal melanoma metastases (LMM) have the worst prognosis and are characterized by rapid disease progression (mean survival 8-10 weeks) and a death from neurological causes. The recent years have seen tremendous progress in the development of targeted and immune therapies for melanoma that has translated into an increased survival benefit. Despite these gains, the majority of patients fail therapy and there is a suspicion that the brain and the leptomeninges are a "sanctuary" sites for melanoma cells that escape both targeted therapy and immunologic therapies. Emerging evidence suggests that (1) Cancer cells migrating to the CNS may have unique molecular properties and (2) the CNS/leptomeningeal microenvironment represents a pro-survival niche that influences therapeutic response. In this Mini-Review, we will outline the clinical course of LMM development and will describe how the intracranial immune and cellular microenvironments offer both opportunities and challenges for the successful management of this disease. We will further discuss the latest data demonstrating the potential use of BRAF inhibitors and immune therapy in the management of LMM, and will review future potential therapeutic strategies for the management of this most devastating complication of advanced melanoma.

M011L-deficient oncolytic myxoma virus induces apoptosis in brain tumor-initiating cells and enhances survival in a novel immunocompetent mouse model of glioblastoma

BACKGROUND

Myxoma virus (MYXV) is a promising oncolytic agent and is highly effective against immortalized glioma cells but less effective against brain tumor initiating cells (BTICs), which are believed to mediate glioma development/recurrence. MYXV encodes various proteins to attenuate host cell apoptosis, including an antiapoptotic Bcl-2 homologue known as M011L. Such proteins may limit the ability of MYXV to kill BTICs, which have heightened resistance to apoptosis. We hypothesized that infecting BTICs with an M011L-deficient MYXV construct would overcome BTIC resistance to MYXV.

METHODS

We used patient-derived BTICs to evaluate the efficacy of M011L knockout virus (vMyx-M011L-KO) versus wild-type MYXV (vMyx-WT) and characterized the mechanism of virus-induced cell death in vitro. To extend our findings in a novel immunocompetent animal model, we derived, cultured, and characterized a C57Bl/6J murine BTIC (mBTIC0309) from a spontaneous murine glioma and evaluated vMyx-M011L-KO efficacy with and without temozolomide (TMZ) in mBTIC0309-bearing mice.

RESULTS

We demonstrated that vMyx-M011L-KO induces apoptosis in BTICs, dramatically increasing sensitivity to the virus. vMyx-WT failed to induce apoptosis as M011L protein prevented Bax activation and cytochrome c release. In vivo, intracranial implantation of mBTIC0309 generated tumors that closely recapitulated the pathological and molecular profile of human gliomas. Treatment of tumor-bearing mice with vMyx-M011L-KO significantly prolonged survival in immunocompetent-but not immunodeficient-mouse models, an effect that is significantly enhanced in combination with TMZ.

CONCLUSIONS

Our data suggest that vMyx-M011L-KO is an effective, well-tolerated, proapoptotic oncolytic virus and a strong candidate for clinical translation.

Analgesic use and the risk of primary adult brain tumor

Glioma and meningioma are uncommon tumors of the brain with few known risk factors. Regular use of aspirin has been linked to a lower risk of gastrointestinal and other cancers, though evidence for an association with brain tumors is mixed. We examined the association of aspirin and other analgesics with the risk of glioma and meningioma in a large US case-control study. Cases were persons recently diagnosed with glioma or meningioma and treated at medical centers in the southeastern US. Controls were persons sampled from the same communities as the cases combined with friends and other associates of the cases. Information on past use of analgesics (aspirin, other anti-inflammatory agents, and acetaminophen) was collected in structured interviews. Logistic regression was used to estimate odds ratios (ORs) and 95 % confidence intervals (CIs) for analgesic use adjusted for potential confounders. All associations were considered according to indication for use. A total of 1123 glioma cases, 310 meningioma cases and 1296 controls were included in the analysis. For indications other than headache, glioma cases were less likely than controls to report regular use of aspirin (OR 0.69; CI 0.56, 0.87), in a dose-dependent manner (P trend < 0.001). No significant associations were observed with other analgesics for glioma, or any class of pain reliever for meningioma. Results suggest that regular aspirin use may reduce incidence of glioma.