Temporal muscle thickness (TMT) was investigated as a novel surrogate marker on MRI examinations of the brain, to detect patients who may be at risk for sarcopenia. TMT was analyzed in a retrospective, normal collective cohort (n = 624), to establish standard reference values. These reference values were correlated with grip strength measurements and body mass index (BMI) in 422 healthy volunteers and validated in a prospective cohort (n = 130) of patients with various neurological disorders. Pearson correlation revealed a strong association between TMT and grip strength (retrospective cohort, ρ = 0.746; p < 0.001; prospective cohort, ρ = 0.649; p < 0.001). A low or no association was found between TMT and age (retrospective cohort, R² correlation coefficient 0.20; p < 0.001; prospective cohort, ρ = −0.199; p = 0.023), or BMI (retrospective cohort, ρ = 0.116; p = 0.042; prospective cohort, ρ = 0.227; p = 0.009), respectively. Male patients with temporal wasting and unintended weight loss, respectively, showed significantly lower TMT values (p = 0.04 and p = 0.015, unpaired t-test). TMT showed a high correlation with muscle strength in healthy individuals and in patients with various neurological disorders. Therefore, TMT should be integrated into the diagnostic workup of neurological patients, to prevent, delay, or treat sarcopenia.

Immunotherapies against brain metastases have shown clinical benefits when applied to asymptomatic patients, but they are largely ineffective in symptomatic cases for unknown reasons. Here, we dissect the heterogeneity in metastasis-associated astrocytes using single-cell RNA sequencing and report a population that blocks the antitumoral activity of infiltrating T cells. This protumoral activity is mediated by the secretion of tissue inhibitor of metalloproteinase-1 (TIMP1) from a cluster of pSTAT3+ astrocytes that acts on CD63+ CD8+ T cells to modulate their function. Using genetic and pharmacologic approaches in mouse and human brain metastasis models, we demonstrate that combining immune checkpoint blockade antibodies with the inhibition of astrocyte-mediated local immunosuppression may benefit patients with symptomatic brain metastases. We further reveal that the presence of tissue inhibitor of metalloproteinase-1 in liquid biopsies provides a biomarker to select patients for this combined immunotherapy. Overall, our findings demonstrate an unexpected immunomodulatory role for astrocytes in brain metastases with clinical implications. Significance: This study presents a significant advancement in understanding immune modulation in brain tumors and offers new insights into the potential therapeutic interventions for brain metastases. See related commentary by Lorger and James, p. 11

An accurate classification of patients with brain metastases (BMs) is an important foundation to guide individualised treatment decisions and to formulate BM cohorts for modern clinical trials. Six thousand and thirty-one patients with newly diagnosed BM from different solid tumours treated between 1986 and 2020 were identified from the Vienna Brain Metastasis Registry. A rising fraction of patients presented with asymptomatic BM during the observation period (1986-1999: 20.2% vs 2010-2020: 30.6%; p < 0.001). Especially, oncogene-addicted non-small-cell lung cancer (NSCLC) and BRAF (v-Raf murine sarcoma viral oncogene homolog)-positive melanoma had a higher rate of asymptomatic BM presentation compared with wild-type tumours (p < 0.05). Significant changes of initial BM treatment approaches were observed with a decrease of neurosurgical procedures (1986-1999: 30.8% vs 2010-2020: 19.5%) and an increase of radiation treatments (1986-1999: 65.0% vs 2010-2020: 73.3%) and systemic therapies (1986-1999: 1.0% vs 2010-2020: 2.0%; p < 0.001). Median overall survival (OS) was heterogeneous between primary tumour entities but with an overall increase over the decades (median OS 1986-1999: 5 months vs 2010-2020: 7 months; p = 0.001). Survival times were longer in patients with oncogene-addicted NSCLC, BRAF-positive melanoma and hormone receptor-positive breast cancer compared with the other cancer subtypes (p > 0.05). Our data highlight shifting trends in the symptomatic presentation and in treatment strategies of patients with BM over the last decades. Entity specific aspects and, in particular, the presence of targetable driver mutation impact the clinical presentation and prognosis. Future BM specific trials need to address the modern composition of BM cohorts and the distinct clinical course of patients with targetable driver mutations.

Purpose: Human malignant pleural mesothelioma (MPM) is characterized by dismal prognosis. Consequently, dissection of molecular mechanisms driving malignancy is of key importance. Here we investigate, whether activating mutations in the telomerase reverse transcriptase (TERT) gene promoter are present in MPM and associated with disease progression, cell immortalization, and genomic alteration patterns. Experimental Design: TERT promoters were sequenced in 182 MPM samples and compared to clinicopathological characteristics. Surgical specimens from 45 MPM patients were tested for in vitro immortalization. The respective MPM cell models (N=22) were analyzed by array comparative genomic hybridization, gene expression profiling, exome sequencing, as well as TRAP, telomere length and luciferase promoter assays. Results: TERT promoter mutations were detected in 19/182 (10.4%) MPM cases and significantly associated with advanced disease and non-epithelioid histology. Mutations independently predicted shorter overall survival in both histological MPM subtypes. Moreover, 9/9 (100%) mutated but only 13/36 (36.1%) wild-type samples formed immortalized cell lines. TERT promoter mutations were associated with enforced promoter activity and TERT mRNA expression, while neither telomerase activity nor telomere lengths were significantly altered. TERT promoter-mutated MPM cases exhibited distinctly reduced chromosomal alterations and specific mutation patterns. While BAP1 mutations/deletions were exclusive with TERT promoter mutations, homozygous deletions at the RBFOX1 and the GSTT1 loci were clearly enriched in mutated cases. Conclusions: TERT promoter mutations independently predict a dismal course of disease in human MPM. The altered genomic aberration pattern indicates that TERT promoter mutations identify a novel, highly aggressive MPM subtype presumably based on a specific malignant transformation process.

Purpose: HER3 belongs to a family of receptor tyrosine kinases with oncogenic properties and is targeted by a variety of novel anticancer agents. There is a huge unmet medical need for systemic treatment options in patients with brain metastases (BM). Therefore, we aimed to investigate HER3 expression in BM of breast (BCa) and non–small cell lung cancer (NSCLC) as the basis for future clinical trial design. Experimental Design: We analyzed 180 BM samples of breast cancer or NSCLC and 47 corresponding NSCLC extracranial tissue. IHC was performed to evaluate protein expression of HER3, and immune cells based on CD3, CD8, and CD68. To identify dysregulated pathways based on differential DNA methylation patterns, we used Infinium MethylationEPIC microarrays. Results: A total of 99/132 (75.0%) of BCa-BM and 35/48 (72.9%) of NSCLC-BM presented with HER3 expression. Among breast cancer, HER2-positive and HER2-low BM showed significantly higher rates of HER3 coexpression than HER2-negative BM (87.1%/85.7% vs. 61.0%, P = 0.004). Among NSCLC, HER3 was more abundantly expressed in BM than in matched extracranial samples (72.9% vs. 41.3%, P = 0.003). No correlation of HER3 expression and intratumoral immune cell density was observed. HER3 expression did not correlate with overall survival from BM diagnosis. Methylation signatures differed according to HER3 status in BCa-BM samples. Pathway analysis revealed subtype-specific differences, such as TrkB and Wnt signaling pathways dysregulated in HER2-positive and triple-negative breast cancer BM, respectively. Conclusions: HER3 is highly abundant in BM of breast cancer and NSCLC. Given the promising results of antibody–drug conjugates in extracranial disease, BM-specific trials that target HER3 are warranted. See related commentary by Kabraji and Lin, p. 2961

Brain metastases (BM) in patients with thyroid cancer (TC) are rare with an incidence of 1% for papillary and follicular, 3% for medullary and up to 10% for anaplastic TC (PTC, FTC, MTC and ATC). Little is known about the characteristics and management of BM from TC. Thus, we retrospectively analyzed patients with histologically verified TC and radiologically verified BM identified from the Vienna Brain Metastasis Registry. A total of 20/6074 patients included in the database since 1986 had BM from TC and 13/20 were female. Ten patients had FTC, 8 PTC, one MTC and one ATC. The median age at diagnosis of BM was 68 years. All but one had symptomatic BM and 13/20 patients had a singular BM. Synchronous BM at primary diagnosis were found in 6 patients, while the median time to BM diagnosis was 13 years for PTC (range 1.9–24), 4 years for FTC (range 2.1–41) and 22 years for the MTC patient. The overall survival from diagnosis of BM was 13 months for PTC (range 1.8–57), 26 months for FTC (range 3.9–188), 12 years for the MTC and 3 months for the ATC patient. In conclusion, development of BM from TC is exceedingly rare and the most common presentation is a symptomatic single lesion. While BM generally constitute a poor prognostic factor, individual patients experience long-term survival following local therapy.