Brain Metastasis from Unknown Primary Tumour: Moving from Old Retrospective Studies to Clinical Trials on Targeted Agents

From pre-clinical to translational brain metastasis research: current challenges and emerging opportunities

Brain metastasis, characterized by poor clinical outcomes, is a devastating disease. Despite significant mechanistic and therapeutic advances in recent years, pivotal improvements in clinical interventions have remained elusive. The heterogeneous nature of the primary tumor of origin, complications in drug delivery across the blood-brain barrier, and the distinct microenvironment collectively pose formidable clinical challenges in developing new treatments for patients with brain metastasis. Although current preclinical models have deepened our basic understanding of the disease, much of the existing research on brain metastasis has employed a reductionist approach. This approach, which often relies on either in vitro systems or in vivo injection models in young and treatment-naive mouse models, does not give sufficient consideration to the clinical context. Given the translational importance of brain metastasis research, we advocate for the design of preclinical experimental models that take into account these unique clinical challenges and align more closely with current clinical practices. We anticipate that aligning and simulating real-world patient conditions will facilitate the development of more translatable treatment regimens. This brief review outlines the most pressing clinical challenges, the current state of research in addressing them, and offers perspectives on innovative metastasis models and tools aimed at identifying novel strategies for more effective management of clinical brain metastasis.

Dose-Incorporated Deep Ensemble Learning for Improving Brain Metastasis Stereotactic Radiosurgery Outcome Prediction

PURPOSE

To develop a novel deep ensemble learning model for accurate prediction of brain metastasis (BM) local control outcomes after stereotactic radiosurgery (SRS).

METHODS AND MATERIALS

A total of 114 brain metastases (BMs) from 82 patients were evaluated, including 26 BMs that developed biopsy-confirmed local failure post-SRS. The SRS spatial dose distribution (Dmap) of each BM was registered to the planning contrast-enhanced T1 (T1-CE) magnetic resonance imaging (MRI). Axial slices of the Dmap, T1-CE, and planning target volume (PTV) segmentation (PTVseg) intersecting the BM center were extracted within a fixed field of view determined by the 60% isodose volume in Dmap. A spherical projection was implemented to transform planar image content onto a spherical surface using multiple projection centers, and the resultant T1-CE/Dmap/PTVseg projections were stacked as a 3-channel variable. Four Visual Geometry Group (VGG-19) deep encoders were used in an ensemble design, with each submodel using a different spherical projection formula as input for BM outcome prediction. In each submodel, clinical features after positional encoding were fused with VGG-19 deep features to generate logit results. The ensemble's outcome was synthesized from the 4 submodel results via logistic regression. In total, 10 model versions with random validation sample assignments were trained to study model robustness. Performance was compared with (1) a single VGG-19 encoder, (2) an ensemble with a T1-CE MRI as the sole image input after projections, and (3) an ensemble with the same image input design without clinical feature inclusion.

RESULTS

The ensemble model achieved an excellent area under the receiver operating characteristic curve (AUCROC: 0.89 ± 0.02) with high sensitivity (0.82 ± 0.05), specificity (0.84 ± 0.11), and accuracy (0.84 ± 0.08) results. This outperformed the MRI-only VGG-19 encoder (sensitivity: 0.35 ± 0.01, AUCROC: 0.64 ± 0.08), the MRI-only deep ensemble (sensitivity: 0.60 ± 0.09, AUCROC: 0.68 ± 0.06), and the 3-channel ensemble without clinical feature fusion (sensitivity: 0.78 ± 0.08, AUCROC: 0.84 ± 0.03).

CONCLUSIONS

Facilitated by the spherical image projection method, a deep ensemble model incorporating Dmap and clinical variables demonstrated excellent performance in predicting BM post-SRS local failure. Our novel approach could improve other radiation therapy outcome models and warrants further evaluation.

Plan quality assessment of modern radiosurgery technologies in the treatment of multiple brain metastases

Stereotactic radiosurgery (SRS) of multiple brain metastases has evolved over the last 40 years allowing centres to treat an increasing number of brain metastases in a single treatment fraction. HyperArcTMplanning optimisation technique is one such development that streamlines the treatment of multiple metastases with a single isocentre. Several studies have investigated the plan quality of HyperArc compared to CyberKnife or Gamma Knife, however there are limited number of studies that include all three modalities. It is the aim of this study to provide an assessment of plan quality between the three SRS platforms across ten patients with multiple brain metastases ranging from three to eight metastases per patient. Strict planning workflows were established to avoid bias towards any particular treatment platform. Plan quality was assessed through dose to organs at risk, Paddick conformity index (PCI), gradient index (GI), global efficiency index (Gη) and dose to normal brain tissue. Results from this study found mean PCI observed across Gamma Knife plans was significantly lower than HyperArc and CyberKnife. HyperArc plans observed significantly shorter beam-on times which were 10 to 20 times faster than CyberKnife and Gamma Knife plans. Gamma Knife and CyberKnife were found to produce plans with significantly superior GI, global efficiency index and the volume of healthy brain receiving greater than 12 Gy (V12Gy) when compared to HyperArc plans. Lesion volume was seen to influence the relative difference in dose metrics between systems. The study revealed that all three treatment modalities produced high quality plans for the SRS treatment of multiple brain metastases, each with respective benefits and limitations.

A comparative study of whole brain radiotherapy with concomitant thalidomide versus whole brain radiotherapy alone in brain metastases

BACKGROUND

Brain metastasis increases morbidity and mortality in cancer patients. This study was undertaken to compare tumor response and treatment-related toxicities in patients treated with orally administered thalidomide concomitantly with whole brain radiotherapy to whole brain radiotherapy alone in brain metastases.

METHODS

This randomized control trial was conducted in radiation oncology department, RIMS among 42 patients of brain metastases distributed in two study arms during the period August 2018 to July 2020. Twenty patients in Arm-A received whole brain radiotherapy to a dose of 3,750 cGy in 15 fractions with concomitant oral thalidomide 200 mg daily in first week and 400 mg/day from second week of radiation onward till the end of radiotherapy, whereas 20 patients of Arm-B received whole brain radiation of 3,750 cGy in 15 fractions alone.

RESULTS

Patient characteristics were comparable. Median central nervous system progression free survival was 2 months for Arm-A and 3 months for Arm-B, whereas median overall survival study was 4 months for Arm-A and 3 months for Arm-B. Overall response rate in Arm-A was 56% and in Arm-B was 44%. Treatment-related toxicities were more in arm-A but were manageable.

CONCLUSION

Addition of thalidomide to whole brain radiotherapy makes no significant difference. Though not statistically significant, but still, Arm-A had shown some percentage benefits. Further studies with larger sample sizes should be done.

Non-colloid-cyst primary brain tumors: A systematic review of unexpected fatality

OBJECTIVE

Primary brain tumors have the potential to present a substantial health hazard, ultimately resulting in unforeseen fatalities. Despite the enhanced comprehension of many diseases, the precise prediction of disease progression continues to pose a significant challenge. The objective of this study is to investigate cases of unexpected mortality resulting from primary brain tumors and analyze the variables that contribute to such occurrences.

METHODS

This systematic review explores research on individuals diagnosed with primary brain tumors who experienced unexpected deaths. It uses PRISMA standards and searches PubMed, Google Scholar, and Scopus. Variables considered include age, gender, symptoms, tumor type, WHO grade, postmortem findings, time of death - time taken from first medical presentation or hospital admission to death, comorbidity, and risk factors.

RESULTS

This study examined 46 studies to analyze patient-level data from 76 individuals with unexpected deaths attributed to intracranial lesions, deliberately excluding colloid cysts. The cohort's age distribution showed an average age of 37 years, with no significant gender preference. Headache was the most common initial symptom. Astrocytomas, meningiomas, and glioblastoma were the most common lesions, while the frontal lobe, temporal lobe, and cerebellum were common locations. Meningiomas and astrocytomas showed faster deaths within the first hour of hospital admission.

CONCLUSION

The etiology of unforeseen fatalities resulting from cerebral tumors elucidates an intricate and varied phenomenon. Although unexpected deaths account for a very tiny proportion of total fatalities, it is probable that their actual occurrence is underestimated as a result of underreporting and misdiagnosis.

Patient reported outcomes following whole brain radiotherapy in patients with brain metastases in NSIA-LUTH Cancer Center

BACKGROUND

Brain metastases (BM) are a common complication in advanced cancer patients, and extremely challenging to treat. Consequently, whole brain radiotherapy (WBRT) remains the standard palliative intervention for patients with BM. The present study set to evaluate the clinical benefits of WBRT by assessing the quality of life (QoL) in WBRT-treated patients with BM, in Nigeria.

METHODS

This was a prospective, longitudinal, hospital-based single-centre study. Consecutive sampling methodology was used to recruit 52 patients with BM undergoing WBRT. Patients were followed up on days 7, 30, 90 and 180 after WBRT. The EORTC QLQ-C15-PAL and EORTC QLQ-BN20 were employed to report patients' responses. The likert scale responses were linearly converted into 0 - 100 scores, and the descriptive analysis was conducted using IBM SPSS Statistics 29.0, at 95% confidence interval, using the two-tailed t-test for continuous variables or the chi-square test for categorical values. The overall survival was calculated with the Kaplan Maier method and the difference tested with Log-rank method, considering the interval from the baseline until death or end of the study.

RESULTS

The study cohort was predominantly females (82.7%), and accordingly, 65.4% of the respondents had a breast primary tumor. A goodness-of-fit test yielded non-significant Chi square Pearson (p = 0.325) and Deviance (p = 1.000) residuals, indicating the best fit. The median overall survival was 180 days (~ 6 months). A total of 20 patients (38%) that survived up to 180 days reported alleviated symptoms and better functioning. A significant improvement in physical functioning (p < 0.001) and emotional functioning (p = 0.031) was reported at 180 days post WBRT, compared to baseline.

CONCLUSIONS

WBRT is an effective palliative intervention in patients with BM, resulting in improved QoL. More than 50% of patients that survived ~ 3 months reported alleviation of pain, and 38% of patients that survived for ~ 6 months reported a significantly improved functioning. This demonstrated the clinical benefits of WBRT in palliative care and will add to the body of data on the use of WBRT, from Africa.

Role of intraoperative touch imprint cytology and immunohistochemistry in the diagnosis of metastatic malignancies in the central nervous system: Cyto-histomorphological findings and differential diagnosis

BACKGROUND

Brain metastases (BMs) are intracranial neoplasms that are more common in adults than primary brain tumors, causing significant mortality and morbidity in cancer patients. This study aimed to evaluate the definitive histopathological diagnosis using touch imprint cytology and the importance and use of immunohistochemistry in the diagnosis of primary origin.

METHOD

Cytological, paraffin section, and immunohistochemical study slides of all metastatic brain tumors consecutively consulted at the pathology department between 2018 and 2023 were evaluated. The sensitivity, specificity, and accuracy of patients' diagnostic results who underwent imprint cytology were compared based on the final diagnosis histopathological report.

RESULTS

A total of 45 patients with and without intraoperative consultation were included in the study. The definitive histopathologic diagnosis and the diagnostic accuracy rate of imprint cytology for distinguishing glial and metastatic tumors on paraffin sections was 100%. Immunohistochemistry was performed in all patients (except one patient; immediate exitus) and histological classification of the primary tumor was performed by analysis of clinical findings and biomarkers. The primary origins of metastatic tumors were often lung and breast, with adenocarcinoma subtype histomorphology, cerebral hemispheres, and discrete foci of metastasis.

CONCLUSION

TPs is a simple and rapid technique that supports diagnosis in intraoperative neuropathology and is a very cost-effective procedure. The pathologist's experience is the key factor in the diagnosis and reduces the need for a frozen section. In our series, the final histopathologic correlation of imprint cytology in the diagnosis of primary and metastatic tumors is 100%.

The role of the neurologist in the diagnosis and treatment of brain metastases and carcinomatous meningitis

Traditionally, in the past, most of central nervous system metastases from solid tumors were associated with an advanced phase of the disease needing palliation only, while to date they increasingly develop as an early and/or solitary relapse in patients with the systemic disease under control. This review will cover all the aspects of a modern management of brain and leptomeningeal metastases from diagnosis to the different therapeutic options, either local (surgery, stereotactic radiosurgery, whole-brain radiotherapy with hippocampal avoidance) or systemic. Particular emphasis is reserved to the new-targeted drugs, that allow to target specifically driver molecular alterations. These new compounds pose new problems in terms of monitoring efficacy and adverse events, but increasingly they allow improvement of outcome in comparison to historical controls.

Deep Learning for Detecting Brain Metastases on MRI: A Systematic Review and Meta-Analysis

Since manual detection of brain metastases (BMs) is time consuming, studies have been conducted to automate this process using deep learning. The purpose of this study was to conduct a systematic review and meta-analysis of the performance of deep learning models that use magnetic resonance imaging (MRI) to detect BMs in cancer patients. A systematic search of MEDLINE, EMBASE, and Web of Science was conducted until 30 September 2022. Inclusion criteria were: patients with BMs; deep learning using MRI images was applied to detect the BMs; sufficient data were present in terms of detective performance; original research articles. Exclusion criteria were: reviews, letters, guidelines, editorials, or errata; case reports or series with less than 20 patients; studies with overlapping cohorts; insufficient data in terms of detective performance; machine learning was used to detect BMs; articles not written in English. Quality Assessment of Diagnostic Accuracy Studies-2 and Checklist for Artificial Intelligence in Medical Imaging was used to assess the quality. Finally, 24 eligible studies were identified for the quantitative analysis. The pooled proportion of patient-wise and lesion-wise detectability was 89%. Articles should adhere to the checklists more strictly. Deep learning algorithms effectively detect BMs. Pooled analysis of false positive rates could not be estimated due to reporting differences.

Small RNA Sequencing Identifies a Six-MicroRNA Signature Enabling Classification of Brain Metastases According to their Origin

BACKGROUND/AIM

Brain metastases (BMs) are the most frequent intracranial tumors in adults and one of the greatest challenges for modern oncology. Most are derived from lung, breast, renal cell, and colorectal carcinomas and melanomas. Up to 14% of patients are diagnosed with BMs of unknown primary, which are commonly characterized by an early and aggressive metastatic spread. It is important to discover novel biomarkers for early identification of BM origin, allowing better management of patients with this disease. Our study focused on microRNAs (miRNAs), which are very stable in frozen native and FFPE tissues and have been shown to be sensitive and specific diagnostic biomarkers of cancer. We aimed to identify miRNAs with significantly different expression in the five most frequent groups of BMs and develop a diagnostic classifier capable of sensitive and specific classification of BMs.

MATERIALS AND METHODS

Total RNA enriched for miRNAs was isolated using the mirVana miRNA Isolation Kit from 71 fresh-frozen histopathologically confirmed BM tissues originating in 5 cancer types. Sequencing libraries were prepared using the QIAseq miRNA Library Kit and sequenced on the NextSeq 500 platform. MiRNA expression was further validated by RT-qPCR.

RESULTS

Differential analysis identified 373 miRNAs with significantly different expression between 5 BM groups (p<0.001). A classifier model was developed based on the expression of 6 miRNAs (hsa-miR-141-3p, hsa-miR-141-5p, hsa-miR-146a-5p, hsa-miR-194-5p, hsa-miR-200b-3p and hsa-miR-365b-5p) with the ability to correctly classify 91.5% of samples. Subsequent validation confirmed both significantly different expression of selected miRNAs in 5 BM groups as well as their diagnostic potential.

CONCLUSION

To date, our study is the first to analyze miRNA expression in various types of BMs using small RNA sequencing to develop a diagnostic classifier and, thus, to help stratify BMs of unknown primary. The presented results confirm the importance of studying the dysregulated expression of miRNAs in BMs and the diagnostic potential of the validated 6-miRNA signature.

Novel Therapeutic Approaches in Neoplastic Meningitis

Central nervous system (CNS) metastasis from systemic cancers can involve the brain parenchyma, leptomeninges, or the dura. Neoplastic meningitis (NM), also known by different terms, including leptomeningeal carcinomatosis and carcinomatous meningitis, occurs due to solid tumors and hematologic malignancies and is associated with a poor prognosis. The current management paradigm entails a multimodal approach focused on palliation with surgery, radiation, and chemotherapy, which may be administered systemically or directly into the cerebrospinal fluid (CSF). This review focuses on novel therapeutic approaches, including targeted and immunotherapeutic agents under investigation, that have shown promise in NM arising from solid tumors.

Prognostic factors among patients with brain metastases from cancer of unknown primary site

PURPOSE

Cancers of an unknown primary site (CUPs) have a dismal prognosis, and the situation is even worse for CUPs patients with brain metastases (BM-CUPs). This study aims to give better insight into the occurrence and survival of BM-CUPs patients.

METHODS

Cases were selected from the Netherlands Cancer Registry (1,430 BM-CUPs/17,140 CUPs). Baseline characteristics between CUPs patients with and without BM were tested using chi-square tests and Mann-Whitney U tests. Patients' overall survival (OS) times were estimated by the Kaplan-Meier method and prognostic factors on OS was assessed using Cox proportional hazards regression analyses.

RESULTS

The proportion of BM-CUPs patients among CUPs increased from 8% in 2009-2010 to 10% in 2017-2018 (p < 0.001). Most patients presented with multiple brain lesions (53%). Survival of BM-CUPs improved over time: one-year OS increased from 10% for patients diagnosed in 2009-2010 to 17% (2017- 2018) (p < 0.01), and median survival times increased from 1.8 months to 2.2 months. Independent predictors of poor survival were multiple (HR 1.25; p < 0.01) or unknown (HR 1.48; p < 0.01) locations of BM, unknown/poorly/undifferentiated carcinoma histology (HR 1.53; p < 0.01), or clinical symptoms of BM (HR 1.74; p < 0.01), accompanying liver metastasis (HR 1.43; p < 0.01) and more than one metastatic site outside the brain compared to none (HR 1.52; p < 0.01).

CONCLUSION

The incidence of patients with BM-CUPs is steadily increasing over time and overall prognosis remains dismal. Our results, however, show distinct patient subgroups that exhibit comparatively better outcomes, and more predictors may likely still be identified.

Brain and Adrenal Metastasis From Unknown Primary Tumor: A Case Report

The clinical management of brain metastasis (BM) and adrenal metastasis (AM) of cancer of unknown primary (CUP) can be challenging. A 73-year-old man presented to the hospital with sudden-onset hemiplegia. His laboratory data were normal, except for elevated levels of carcinoembryonic antigen (CEA) (33.8 ng/mL). Contrast-enhanced magnetic resonance imaging revealed a 2-cm mass with ring enhancement in the right parietal lobe and extensive vasogenic edema around the tumor. The lesion was diagnosed as BM; however, we could not detect the primary origin by fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT). Stereotactic radiotherapy was then administered, resulting in reduced tumor size and relief of symptoms. Follow-up after one year revealed an elevated CEA level (148.6 ng/mL) and remarkable fluorodeoxyglucose (FDG) uptake in the right adrenal gland, with an area of enhancement of 20 mm, on FDG-positron emission tomography computed tomography, with normal findings in other distant organs. He underwent adrenalectomy, and the adrenal tumor was diagnosed as a poorly differentiated adenocarcinoma likely of lung origin based on the histopathologic and immunohistochemistry findings of cytokeratin (CK) 7 (+), CK 20 (-), thyroid transcription factor-1 (TTF-1) (+), inhibin (-), napsin A (+), prostate-specific antigen (PSA) (-), caudal type homeobox 2 (CDX-2) (-), synaptophysin (-), and p40 (-). Metastatic tumors of unknown primary origin remain latent. Aggressive treatment of these lesions can be beneficial for symptom relief, diagnosis, and prolongation of survival.

Current Advances and Challenges in Radiomics of Brain Tumors

Imaging diagnosis is crucial for early detection and monitoring of brain tumors. Radiomics enable the extraction of a large mass of quantitative features from complex clinical imaging arrays, and then transform them into high-dimensional data which can subsequently be mined to find their relevance with the tumor's histological features, which reflect underlying genetic mutations and malignancy, along with grade, progression, therapeutic effect, or even overall survival (OS). Compared to traditional brain imaging, radiomics provides quantitative information linked to meaningful biologic characteristics and application of deep learning which sheds light on the full automation of imaging diagnosis. Recent studies have shown that radiomics' application is broad in identifying primary tumor, differential diagnosis, grading, evaluation of mutation status and aggression, prediction of treatment response and recurrence in pituitary tumors, gliomas, and brain metastases. In this descriptive review, besides establishing a general understanding among protocols, results, and clinical significance of these studies, we further discuss the current limitations along with future development of radiomics.