Laser interstitial thermal therapy for new and recurrent meningioma: a prospective and retrospective case series.

OBJECTIVE: Meningiomas are the most common primary brain tumors in adults and a subset are aggressive lesions resistant to standard therapies. Laser interstitial thermal therapy (LITT) has been successfully applied to other brain tumors, and recent work aims to explore the safety and long-term outcome experiences of LITT for both new and recurrent meningiomas. The authors' objective was to report safety and outcomes data of the largest cohort of LITT-treated meningioma patients to date. METHODS: Eight United States-based hospitals enrolled patients with meningioma in the Laser Ablation of Abnormal Neurological Tissue Using Robotic NeuroBlate System (LAANTERN) prospective multicenter registry and/or contributed additional retrospective enrollments for this cohort study. Demographic, procedural, safety, and outcomes data were collected and analyzed using standard statistical methods. RESULTS: Twenty adult patients (12 prospective and 8 retrospective) with LITT-targeted meningiomas were accrued. Patients underwent LITT for new (6 patients) and recurrent (14 patients) tumors (ranging from the 1st to 12th recurrence). The 30-day complication rate was 10%. Twenty percent of patients (4/20) had exhausted all other treatment options. Median length of follow-up was 1.3 years. One-third of new (2/6) and one-half of recurrent (7/14) meningiomas had disease progression during follow-up. One-year estimated local control (LC), progression-free survival, and overall survival rates were 55.3%, 48.4%, and 86.3%, respectively. In the 12 patients who had ≥ 91% ablative coverage, 1-year estimated LC was 61.4%. The complication rate was 10% (2/20), with 1 complication being transient and resolving postoperatively. CONCLUSIONS: This cohort study supports the safety of the procedure for this tumor type. LITT can offer a much-needed treatment option, especially for patients with multiply recurrent meningiomas who have limited remaining alternatives.

Executive Summary of the American Radium Society Appropriate Use Criteria for Brain Metastases in EGFR-mutated and ALK-fusion Non-Small Cell Lung Cancer.

BACKGROUND: The American Radium Society (ARS) Central Nervous System (CNS) committee reviewed literature on epidermal growth factor receptor mutated (EGFRm) and ALK-fusion (ALK+) tyrosine kinase inhibitors (TKIs) for the treatment of brain metastases (BrMs) from non-small cell lung cancers (NSCLC) to generate appropriate use guidelines addressing use of TKIs in conjunction with or in lieu of radiotherapy (RT). METHODS: The panel developed three key questions to guide systematic review: can radiotherapy be deferred in patients receiving EGFR or ALK TKIs at 1) diagnosis or 2) recurrence? Should TKI be administered concurrently with RT (3)? Two literature searches were performed (May 2019 and December 2023). The panel developed 8 model cases and voted on treatment options using a 9-point scale, with 1-3, 4-6 and 7-9 corresponding to usually not appropriate, may be appropriate, and usually appropriate (respectively), per the UCLA/RAND Appropriateness Method. RESULTS: Consensus was achieved in only 4 treatment scenarios, all consistent with existing ARS-AUC guidelines for multiple BrM. The panel did not reach consensus that RT can be appropriately deferred in patients with BrM receiving CNS penetrant ALK or EGFR TKIs, though median scores indicated deferral may be appropriate under most circumstances. Whole brain RT with concurrent TKI generated broad disagreement except in cases with 2-4 BrM, where it was considered usually not appropriate. CONCLUSIONS: We identified no definitive studies dictating optimal sequencing of TKIs and RT for EGFRm and ALK+ BrM. Until such studies are completed, the committee hopes these cases guide decision-making in this complex clinical space.

Selected-Lesion Stereotactic Radiosurgery (SL-SRS) as a Novel Strategy in the Treatment of Patients With Multiple Brain Metastases.

INTRODUCTION: With the diminishing use of whole-brain radiotherapy (WBRT), there is increasing debate regarding the maximum number of brain metastases that should be treated with stereotactic radiosurgery (SRS). In patients with >10-15 lesions, some groups are proposing a new approach - selected-lesion SRS (SL-SRS) - where only a subset of intracranial lesions are chosen for irradiation. This study is an initial look into this practice. METHODS: This is a cross-sectional exploratory survey study. A survey of 19 questions was created by the International Radiosurgery Research Foundation (IRRF) using open-ended and multiple-choice style questions on SL-SRS practices and indications with the goal of qualitatively understanding how SL-SRS is being implemented worldwide. The survey was distributed to physicians in the United States (US) and internationally who are members of the IRRF and who perform SRS frequently. Ten out of 50 IRRF institutions provided responses reflecting the practices of 16 physicians. RESULTS: SL-SRS is being performed at 8/10 institutions. The most common reasons for using SL-SRS included patients with prior WBRT, patients with progressing systemic disease with central nervous system (CNS)-penetrating or immunotherapies available, specific requests from medical oncology, and cooperative studies using this approach. Lesion size was cited as the most important factor when choosing to irradiate any single lesion. The majority of respondents reported 30 mm and 40 mm as size cutoffs (by largest dimension) for treatment of a lesion in eloquent and non-eloquent locations, respectively. Eloquence of lesion location and attributable symptoms were also considered important. Progression of untreated lesions was the most common reason reported for bringing patients back for additional treatment. CONCLUSION: The responses to this survey show that SL-SRS is being used, allowing for small/asymptomatic brain metastases to be left safely unirradiated. It is currently used in patients who have >10-15 lesions with prior WBRT, those with progression of extracranial disease but with acceptable systemic treatment options, and those with poor functional status. The incorporation of this new approach into clinical trials should be considered for the safe study of the efficacy of new CNS-penetrating systemic therapies.

Management of patients with brain metastases from NSCLC without a genetic driver alteration: upfront radiotherapy or immunotherapy?

Lung cancer is the second most common cancer and the most common cause of cancer-related death in the United States. Brain metastases (BM) are detected in 21% of patients with lung cancer at the time of diagnosis and are the sole metastatic site in 35% of patients with stage IV disease. The best upfront therapy for non-small-cell lung cancer depends on both tumor programmed death 1 ligand-1 (PD-L1) expression and the presence or absence of a targetable genetic alteration in genes such as epidermal growth factor receptor and anaplastic lymphoma kinase. In the absence of a targetable genetic alteration, options include chemotherapy, immune checkpoint inhibitors (ICIs), and ICI combined with chemotherapy. Upfront local therapy followed by systemic therapy is the current standard of care for the management of BM, and may include whole brain radiotherapy, stereotactic radiosurgery (SRS), or craniotomy for surgical resection followed by consolidative SRS. This paradigm is effective in achieving local control, but it remains unclear if this approach is necessary for every patient. Prospective and retrospective data suggest that ICIs with or without chemotherapy can have activity against BM; however, appropriately selecting patients who are able to safely forgo local therapy and start an ICI-based treatment remains a challenge. To be considered for upfront ICI-based therapy, a patient should be free of neurologic symptoms, lesions should be small and not located in a critical region of the central nervous system, if corticosteroids are indicated the requirement should be low (prednisone 10 mg/d or less), and PD-L1 expression should be high. The decision to proceed with upfront ICI without local therapy to BM should be made in a multidisciplinary fashion and patients should undergo frequent surveillance imaging so that salvage local therapy can be administered when necessary. Prospective clinical trials are needed to validate this approach before it can be widely adopted.

Lenvatinib or anti-VEGF in combination with anti-PD-1 differentially augments antitumor activity in melanoma.

Targeting tumor-associated blood vessels to increase immune infiltration may enhance treatment effectiveness, yet limited data exist regarding anti-angiogenesis effects on the tumor microenvironment (TME). We hypothesized that dual targeting of angiogenesis with immune checkpoints would improve both intracranial and extracranial disease. We used subcutaneous and left ventricle melanoma models to evaluate anti-PD-1/anti-VEGF and anti-PD-1/lenvatinib (pan-VEGFR inhibitor) combinations. Cytokine/chemokine profiling and flow cytometry were performed to assess signaling and immune-infiltrating populations. An in vitro blood-brain barrier (BBB) model was utilized to study intracranial treatment effects on endothelial integrity and leukocyte transmigration. Anti-PD-1 with either anti-VEGF or lenvatinib improved survival and decreased tumor growth in systemic melanoma murine models; treatment increased Th1 cytokine/chemokine signaling. Lenvatinib decreased tumor-associated macrophages but increased plasmacytoid DCs early in treatment; this effect was not evident with anti-VEGF. Both lenvatinib and anti-VEGF resulted in decreased intratumoral blood vessels. Although anti-VEGF promoted endothelial stabilization in an in vitro BBB model, while lenvatinib did not, both regimens enabled leukocyte transmigration. The combined targeting of PD-1 and VEGF or its receptors promotes enhanced melanoma antitumor activity, yet their effects on the TME are quite different. These studies provide insights into dual anti-PD-1 and anti-angiogenesis combinations.

Synchronous glioblastoma and brain metastases: illustrative case.

BACKGROUND: Radiosurgical treatment of brain metastases is usually performed without brain tissue confirmation. While it is extremely rare for glioblastoma to develop concurrently in patients with brain metastases, they can look radiographically similar, and recognition is important because it alters management and prognosis. The synchronous presence of brain metastases and glioblastoma has not been published to date in the literature, making this a rare illustrative case. OBSERVATIONS: A 70-year-old female had lung biopsy-proven metastatic lung adenocarcinoma and multiple brain metastases. Her treatment course included initial carboplatin, pemetrexed, and bevacizumab followed by maintenance nivolumab, and she underwent stereotactic radiosurgery to the multiple brain metastases. During interval radiological surveillance, one lesion in the right temporal lobe was noted to slowly progress associated with development of significant perilesional edema causing midline shift despite repeated stereotactic radiosurgical treatments. Biopsy of this lesion revealed glioblastoma, IDH wildtype. LESSONS: Glioblastomas and brain metastases have similar radiological features, so the possibility of incorrect diagnosis needs to be considered for all lesions with interval growth poststereotactic radiosurgery. Biopsy and/or resection/laser ablation should be considered prior to reirradiation.

Histological changes associated with laser interstitial thermal therapy for radiation necrosis: illustrative cases.

BACKGROUND: Patients with lung cancer and melanoma remain the two largest groups to develop brain metastases. Immunotherapy has been approved for treatment of stage IV disease in both groups. Many of these patients are additionally treated with stereotactic radiosurgery for their brain metastases during ongoing immunotherapy. Use of immunotherapy has been reported to increase the rates of radiation necrosis (RN) after radiosurgery, causing neurological compromise due to growth of the enhancing lesion as well as worsening of associated cerebral edema. OBSERVATIONS: Laser interstitial thermal therapy (LITT) is a surgical approach that has been shown effective in the management of RN, especially given its efficacy in early reduction of perilesional edema. However, little remains known about the pathology of the post-LITT lesions and how LITT works in this condition. Here, we present two patients who needed surgical decompression after LITT for RN. Clinical, histopathological, and imaging features of both patients are presented. LESSONS: Criteria for selecting the best patients with RN for LITT therapy remains unclear. Given two similarly sized lesions and not too dissimilar clinical histories but with differing outcomes, further investigation is clearly needed to identify predictors of response to LITT in the setting of SRS and immunotherapy-induced RN.

Combination laser interstitial thermal therapy plus stereotactic radiotherapy increases time to progression for biopsy-proven recurrent brain metastases.

Background: Improved survival for patients with brain metastases has been accompanied by a rise in tumor recurrence after stereotactic radiotherapy (SRT). Laser interstitial thermal therapy (LITT) has emerged as an effective treatment for SRT failures as an alternative to open resection or repeat SRT. We aimed to evaluate the efficacy of LITT followed by SRT (LITT+SRT) in recurrent brain metastases. Methods: A multicenter, retrospective study was performed of patients who underwent treatment for biopsy-proven brain metastasis recurrence after SRT at an academic medical center. Patients were stratified by "planned LITT+SRT" versus "LITT alone" versus "repeat SRT alone." Index lesion progression was determined by modified Response Assessment in Neuro-Oncology Brain Metastases (RANO-BM) criteria. Results: Fifty-five patients met inclusion criteria, with a median follow-up of 7.3 months (range: 1.0-30.5), age of 60 years (range: 37-86), Karnofsky Performance Status (KPS) of 80 (range: 60-100), and pre-LITT/biopsy contrast-enhancing volume of 5.7 cc (range: 0.7-19.4). Thirty-eight percent of patients underwent LITT+SRT, 45% LITT alone, and 16% SRT alone. Median time to index lesion progression (29.8, 7.5, and 3.7 months [P = .022]) was significantly improved with LITT+SRT. When controlling for age in a multivariate analysis, patients treated with LITT+SRT remained significantly less likely to have index lesion progression (P = .004). Conclusions: These data suggest that LITT+SRT is superior to LITT or repeat SRT alone for treatment of biopsy-proven brain metastasis recurrence after SRT failure. Prospective trials are warranted to validate the efficacy of using combination LITT+SRT for treatment of recurrent brain metastases.

Brain metastases: A Society for Neuro-Oncology (SNO) consensus review on current management and future directions.

Brain metastases occur commonly in patients with advanced solid malignancies. Yet, less is known about brain metastases than cancer-related entities of similar incidence. Advances in oncologic care have heightened the importance of intracranial management. Here, in this consensus review supported by the Society for Neuro-Oncology (SNO), we review the landscape of brain metastases with particular attention to management approaches and ongoing efforts with potential to shape future paradigms of care. Each coauthor carried an area of expertise within the field of brain metastases and initially composed, edited, or reviewed their specific subsection of interest. After each subsection was accordingly written, multiple drafts of the manuscript were circulated to the entire list of authors for group discussion and feedback. The hope is that the these consensus guidelines will accelerate progress in the understanding and management of patients with brain metastases, and highlight key areas in need of further exploration that will lead to dedicated trials and other research investigations designed to advance the field.

Executive summary of American Radium Society's appropriate use criteria for the postoperative management of lower grade gliomas.

Postoperative management of lower grade gliomas (grade 2 and 3) is heterogeneous. The American Radium Society's brain malignancies panel systematically reviewed and evaluated the literature to develop consensus guidelines addressing timing of postoperative therapy, monotherapy versus combined modality therapy, type of chemotherapy used with radiotherapy, and radiotherapy dose. Thirty-six studies were included. Using consensus methodology (modified Delphi), the panel voted upon representative case variants using a 9-point appropriateness scale to address key questions. Voting results were collated to develop summarized recommendations. Following gross-total surgical resection, close surveillance is appropriate for well-selected grade 2, IDH-mutant oligodendrogliomas or astrocytomas with low-risk features. For grade 2 gliomas with high-risk features or any grade 3 glioma, immediate adjuvant therapy is recommended. When postoperative therapy is administered, radiation and planned chemotherapy is strongly recommended over monotherapy. For grade 2 and 3 IDH-mutant oligodendrogliomas and astrocytomas, either adjunctive PCV (procarbazine, lomustine, vincristine) or temozolomide is appropriate. For grade 3 IDH-mutant astrocytomas, radiotherapy followed by temozolomide is strongly recommended. The recommended radiotherapy dose for grade 2 gliomas is 45-54 Gy/1.8-2.0 Gy, and for grade 3 gliomas is 59.4-60 Gy/1.8-2.0 Gy. While multiple appropriate treatment options exist, these consensus recommendations provide an evidence-based framework to approach postoperative management of lower grade gliomas.

Machine Learning Applications for Differentiation of Glioma from Brain Metastasis-A Systematic Review.

Glioma and brain metastasis can be difficult to distinguish on conventional magnetic resonance imaging (MRI) due to the similarity of imaging features in specific clinical circumstances. Multiple studies have investigated the use of machine learning (ML) models for non-invasive differentiation of glioma from brain metastasis. Many of the studies report promising classification results, however, to date, none have been implemented into clinical practice. After a screening of 12,470 studies, we included 29 eligible studies in our systematic review. From each study, we aggregated data on model design, development, and best classifiers, as well as quality of reporting according to the TRIPOD statement. In a subset of eligible studies, we conducted a meta-analysis of the reported AUC. It was found that data predominantly originated from single-center institutions (n = 25/29) and only two studies performed external validation. The median TRIPOD adherence was 0.48, indicating insufficient quality of reporting among surveyed studies. Our findings illustrate that despite promising classification results, reliable model assessment is limited by poor reporting of study design and lack of algorithm validation and generalizability. Therefore, adherence to quality guidelines and validation on outside datasets is critical for the clinical translation of ML for the differentiation of glioma and brain metastasis.

Factors associated with progression and mortality among patients undergoing stereotactic radiosurgery for intracranial metastasis: results from a national real-world registry.

OBJECTIVE: Stereotactic radiosurgery (SRS) has been increasingly employed in recent years to treat intracranial metastatic lesions. However, there is still a need for optimization of treatment paradigms to provide better local control and prevent progressive intracranial disease. In the current study, the authors utilized a national collaborative registry to investigate the outcomes of patients with intracranial metastatic disease who underwent SRS and to determine factors associated with lesion treatment response, overall progression, and mortality. METHODS: The NeuroPoint Alliance SRS registry was queried for all patients with intracranial metastatic lesions undergoing single- or multifraction SRS at participating institutions between 2016 and 2020. The main outcomes of interest included lesion response (lesion-level analysis), progression using Response Assessment for Neuro-Oncology criteria, and mortality (patient-level analysis). Kaplan-Meier analysis was used to report time to progression and overall survival, and multivariable Cox proportional hazards analysis was used to investigate factors associated with lesion response, progression, and mortality. RESULTS: A total of 501 patients (1447 intracranial metastatic lesions) who underwent SRS and had available follow-up were included in the current analyses. The most common primary tumor was lung cancer (49.5%, n = 248), followed by breast (15.4%, n = 77) and melanoma (12.2%, n = 61). Most patients had a single lesion (44.9%, n = 225), 29.3% (n = 147) had 2 or 3 lesions, and 25.7% (n = 129) had > 3 lesions. The mean sum of baseline measurements of the lesions according to Response Evaluation Criteria in Solid Tumors (RECIST) was 35.54 mm (SD 25.94). At follow-up, 671 lesions (46.4%) had a complete response, 631 (43.6%) had a partial response (≥ 30% decrease in longest diameter) or were stable (< 30% decrease but < 20% increase), and 145 (10%) showed progression (> 20% increase in longest diameter). On multivariable Cox proportional hazards analysis, melanoma-associated lesions (HR 0.48, 95% CI 0.34-0.67; p < 0.001) and larger lesion size (HR 0.94, 95% CI 0.93-0.96; p < 0.001) showed lower odds of lesion regression, while a higher biologically effective dose was associated with higher odds (HR 1.001, 95% CI 1.0001-1.00023; p < 0.001). A total of 237 patients (47.3%) had overall progression (local failure or intracranial progressive disease), with a median time to progression of 10.03 months after the index SRS. Factors found to be associated with increased hazards of progression included male sex (HR 1.48, 95% CI 1.108-1.99; p = 0.008), while administration of immunotherapy (before or after SRS) was found to be associated with lower hazards of overall progression (HR 0.62, 95% CI 0.460-0.85; p = 0.003). A total of 121 patients (23.95%) died during the follow-up period, with a median survival of 19.4 months from the time of initial SRS. A higher recursive partitioning analysis score (HR 21.3485, 95% CI 1.53202-3.6285; p < 0.001) was found to be associated with higher hazards of mortality, while single-fraction treatment compared with hypofractionated treatment (HR 0.082, 95% CI 0.011-0.61; p = 0.015), administration of immunotherapy (HR 0.385, 95% CI 0.233-0.64; p < 0.001), and presence of single compared with > 3 lesions (HR 0.427, 95% CI 0.187-0.98; p = 0.044) were found to be associated with lower risk of mortality. CONCLUSIONS: The comparability of results between this study and those of previously published clinical trials affirms the value of multicenter databases with real-world data collected without predetermined research purpose.

Adverse radiation effects in volume-staged radiosurgery for large arteriovenous malformations: a multiinstitutional study.

OBJECTIVE: The optimal treatment paradigm for large arteriovenous malformations (AVMs) is controversial. One approach is volume-staged stereotactic radiosurgery (VS-SRS). The authors previously reported efficacy of VS-SRS for large AVMs in a multiinstitutional cohort; here they focus on risk of symptomatic adverse radiation effects (AREs). METHODS: This is a multicentered retrospective review of patients treated with a planned prospective volume staging approach to stereotactically treat the entire nidus of an AVM, with volume stages separated by intervals of 3-6 months. A total of 9 radiosurgical centers treated 257 patients with VS-SRS between 1991 and 2016. The authors evaluated permanent, transient, and total ARE events that were symptomatic. RESULTS: Patients received 2-4 total volume stages. The median age was 33 years at the time of the first SRS volume stage, and the median follow-up was 5.7 years after VS-SRS. The median total AVM nidus volume was 23.25 cm3 (range 7.7-94.4 cm3), with a median margin dose per stage of 17 Gy (range 12-20 Gy). A total of 64 patients (25%) experienced an ARE, of which 19 were permanent. Rather than volume, maximal linear dimension in the Z (craniocaudal) dimension was associated with toxicity; a threshold length of 3.28 cm was associated with an ARE, with a 72.5% sensitivity and a 58.3% specificity. In addition, parietal lobe involvement for superficial lesions and temporal lobe involvement for deep lesions were associated with an ARE. CONCLUSIONS: Size remains the dominant predictor of toxicity following SRS, but overall rates of AREs were lower than anticipated based on baseline features, suggesting that dose and size were relatively dissociated through volume staging. Further techniques need to be assessed to optimize outcomes.

Spatially resolved analysis of the T cell immune contexture in lung cancer-associated brain metastases.

Despite unique genetic alterations within brain metastases (BrMs) and an immunologically distinct surrounding microenvironment, the composition and functional properties of tumor-infiltrating lymphocytes within BrM remain largely unexplored. In particular, the expression of coinhibitory receptors, such as programmed cell death 1 (PD-1), T cell immunoglobulin mucin receptor 3 (TIM-3), and lymphocyte activation gene 3 (LAG-3), within BrMs is unknown. Using multiplexed quantitative immunofluorescence (QIF), this study evaluates the localized expression of PD-L1, level and functional profile of major T cell subsets, and coinhibitory receptors within lung cancer-associated BrMs and primary lung tumors. Clinicopathologically annotated samples from 95 patients with lung cancer between 2002 and 2015 were represented in a tissue microarray format. Spatially resolved and multiplexed QIF was used to evaluate PD-L1 protein, phenotype markers for major T cell subsets (CD3, CD4, CD8, and FOXP3), cell-localized activation and proliferation markers (granzyme B and Ki67), and coinhibitory receptors (PD-1, LAG-3, and TIM-3). The signal for each marker was measured in marker-selected tissue compartments, and associations between marker levels, tumor location, and major clinicopathological variables were studied. In total, 41 primary lung tumors and 65 BrMs were analyzed, including paired samples from 11 patients. Levels of tumor PD-L1 expression were comparable between BrMs and primary lung tumors. BrMs had significantly lower levels of all T cell subsets relative to primary lung tumors, and T cells in BrMs displayed lower levels of granzyme B than primary lesions. PD-1, TIM-3, and LAG-3 levels in CD3+ T-cells were also significantly lower in BrMs. Marker expression in patients with paired samples from BrMs and primary lung tumors showed comparable results. High CD3+ T-cells, as well as high levels of TIM-3 and LAG-3 in CD3+ T-cells, were associated with longer overall survival in BrMs but not primary lung tumors. Lung cancer-associated BrMs display lower T cell infiltration, markers of cytolytic function, and immune regulatory signals than primary lung tumors. Despite these differences, high TIM-3 and high LAG-3 expressions in CD3+ T-cells were associated with longer survival. These features are accompanied by comparable levels of PD-L1 protein expression compared with primary lung tumors. These results highlight unique aspects of the tumor immune microenvironment within the brain and provide further support for intracranially focused therapies.

Outcomes of Stereotactic Radiosurgery and Immunotherapy in Renal Cell Carcinoma Patients With Brain Metastases.

OBJECTIVE: The impact of immunotherapy and stereotactic radiosurgery (SRS) in treatment of brain metastases (BM) from renal cell carcinoma (RCC) has not been well investigated. MATERIALS AND METHODS: Forty-eight patients with 372 RCC BM were treated with SRS and divided into those ever treated with immunotherapy versus those who never received immunotherapy. Survival and local control (LC) outcomes were studied. χ2 and Mann-Whitney U tests compared categorical and continuous variables, respectively. Kaplan-Meier curves were used to estimate survival and log-rank test was used to compare survival between groups. RESULTS: Immunotherapy and nonimmunotherapy groups contained 29 and 19 patients, respectively. Median follow-up was 23.1 months (range, 6 to 93.8 mo). Demographic and treatment variables were similar except median prescribed margin dose was significantly lower in immunotherapy group (20 vs. 22 Gy, P<0.0001). Median overall survival (OS) was 27.2 months (immunotherapy) and 14.9 months (nonimmunotherapy), P=0.14. Furthermore, patients treated with immune checkpoint inhibitor (ICI) had even better median OS compared with those who never received ICI (33 vs. 16.7 mo, P=0.03). Factors associated with improved LC were use of ICI (P=0.002) and lesion size <1000 mm3 (P=0.046). There was no difference in incidence of radiation necrosis between the 2 groups (P=0.67). CONCLUSIONS: Patients with RCC BM undergoing SRS can experience prolonged survival when treated with ICI. Equally effective LC of BM was achieved when treated with immunotherapy using a 2 Gy decrease in SRS dose without increasing the risk of central nervous system toxicity.

Incidence and characteristics of metastatic intracranial lesions in stage III and IV melanoma: a single institute retrospective analysis.

INTRODUCTION: The study aimed to describe the brain metastases (BM) incidence, at diagnosis and follow-up, in patients initially presenting with stage III or IV melanoma and characterize their metastatic brain lesions. We also sought to describe the association of common genetic mutations and immunotherapy with BM development in advanced melanoma. METHODS: Using our institution's tumor registry, we identified patients with initial diagnoses of stage III and stage IV melanoma. In this cohort, we obtained BM incidence at diagnosis and follow-up, characterized the metastatic brain lesions and primary tumor's genetic profile. RESULTS: During the follow-up period, 22.9% of patients with an initial diagnosis of stage III developed BM. In this cohort, the median time for BM occurrence was 20 months; [95% CI (14-29)]. Likewise, 37.7% of patients with Stage IV melanoma presented with BM at the time of diagnosis, and 22.7% of remaining patients developed BM at follow-up over a median duration of 6 months [95% CI (4-11)]. Therefore, suggesting an overall incidence of 51.9% in stage IV melanoma. Next, we observed that the incidence of BM development during the follow-up period significantly decreased from 2012 to 2017 (p < 0.001). Lastly, we found a significantly higher frequency of mutational BRAF in the primary tumor of patients with BM (68.7% vs. 31.2%; p = 0.02). CONCLUSIONS: While the overall incidence of BM remains high, the decreasing incidence of BM over the follow-up period is promising. Similar BM incidence in patients with an initial diagnosis of stage III or stage IV warrants appropriate imaging surveillance regimen for stage III patients.

Clinical Significance of PDCD4 in Melanoma by Subcellular Expression and in Tumor-Associated Immune Cells.

Little is known about the subcellular localization and function of programmed cell death 4 (PDCD4) in melanoma. Our past studies suggest PDCD4 interacts with Pleckstrin Homology Domain Containing A5 (PLEKHA5) to influence melanoma brain metastasis outcomes, as high intracranial PDCD4 expression leads to improved survival. We aimed to define the subcellular distribution of PDCD4 in melanoma and in the tumor microenvironment during neoplastic progression and its impact on clinical outcomes. We analyzed multiple tissue microarrays with well-annotated clinicopathological variables using quantitative immunofluorescence and evaluated single-cell RNA-sequencing on a brain metastasis sample to characterize PDCD4+ immune cell subsets. We demonstrate differences in PDCD4 expression during neoplastic progression, with high tumor and stromal PDCD4 levels associated with improved survival in primary melanomas and in intracranial metastases, but not in extracranial metastatic disease. While the expression of PDCD4 is well-documented on CD8+ T cells and natural killer cells, we show that it is also found on B cells and mast cells. PDCD4 expression in the tumor microenvironment is associated with increased immune cell infiltration. Further studies are needed to define the interaction of PDCD4 and PLEKHA5 and to evaluate the utility of this pathway as a therapeutic target in melanoma brain metastasis.

[11C]Methionine and [11C]PBR28 as PET Imaging Tracers to Differentiate Metastatic Tumor Recurrence or Radiation Necrosis.

PURPOSE: As stereotactic radiosurgery (SRS) and immunotherapy are increasingly used to treat brain metastases, incidence of radiation necrosis (RN) is consequently rising. Differentiating tumor regrowth (TR) from RN is vital in management but difficult to assess using MRI. We hypothesized that tumor methionine levels would be elevated given increased metabolism and high amino acid uptake, whereas RN would increase inflammation marked by upregulated translocator protein (PBR-TSPO), which can be quantified with specific PET tracers. PROCEDURES: We performed a feasibility study to prospectively evaluate [11C]methionine and [11C]PBR28 using PET in 5 patients with 7 previously SRS-treated brain metastases demonstrating regrowth to differentiate TR from RN. RESULTS: Sequential imaging with dual tracers was well-tolerated. [11C]methionine was accurate for detecting pathologically confirmed TR in 7/7 lesions, whereas [11C]PBR28 was only accurate in 3/7 lesions. Tumor PBR-TSPO expression was elevated in both melanoma and lung cancer cells, contributing to lack of specificity of [11C]PBR28-PET. CONCLUSION: Sequential use of PET tracers is safe and effective. [11C]Methionine was a reliable TR marker, but [11C]PBR28 was not a reliable marker of RN. Studies are needed to determine the causes of post-radiation inflammation and identify specific markers of RN to improve diagnostic imaging.