Faculty Bibliography

Effective diagnosis, prognostication, and management of CNS malignancies traditionally involves invasive brain biopsies that pose significant risk to the patient. Sampling and molecular profiling of cerebrospinal fluid (CSF) is a safer, rapid, and noninvasive alternative that offers a snapshot of the intracranial milieu while overcoming the challenge of sampling error that plagues conventional brain biopsy. Although numerous biomarkers have been identified, translational challenges remain, and standardization of protocols is necessary. Here, we systematically reviewed 141 studies (Medline, SCOPUS, and Biosis databases; between January 2000 and September 29, 2022) that molecularly profiled CSF from adults with brain malignancies including glioma, brain metastasis, and primary and secondary CNS lymphomas. We provide an overview of promising CSF biomarkers, propose CSF reporting guidelines, and discuss the various considerations that go into biomarker discovery, including the influence of blood-brain barrier disruption, cell of origin, and site of CSF acquisition (eg, lumbar and ventricular). We also performed a meta-analysis of proteomic data sets, identifying biomarkers in CNS malignancies and establishing a resource for the research community.

BACKGROUND:For elderly patients with high-grade gliomas, 3-week hypofractionated radiotherapy (HFRT) is noninferior to standard long-course radiotherapy (LCRT). We analyzed real-world utilization of HFRT with and without systemic therapy in Medicare beneficiaries treated with RT for primary central nervous system (CNS) tumors using Centers for Medicare & Medicaid Services data. METHODS:Radiation modality, year, age (65-74, 75-84, or ≥85 years), and site of care (freestanding vs hospital-affiliated) were evaluated. Utilization of HFRT (11-20 fractions) versus LCRT (21-30 or 31-40 fractions) and systemic therapy was evaluated by multivariable logistic regression. Medicare spending over the 90-day episode after RT planning initiation was analyzed using multivariable linear regression. RESULTS:From 2015 to 2019, a total of 10,702 RT courses (ie, episodes) were included (28% HFRT; 65% of patients aged 65-74 years). A considerable minority died within 90 days of RT planning initiation (n=1,251; 12%), and 765 (61%) of those received HFRT. HFRT utilization increased (24% in 2015 to 31% in 2019; odds ratio [OR], 1.2 per year; 95% CI, 1.1-1.2) and was associated with older age (≥85 vs 65-74 years; OR, 6.8; 95% CI, 5.5-8.4), death within 90 days of RT planning initiation (OR, 5.0; 95% CI, 4.4-5.8), hospital-affiliated sites (OR, 1.4; 95% CI, 1.3-1.6), conventional external-beam RT (vs intensity-modulated RT; OR, 2.7; 95% CI, 2.3-3.1), and no systemic therapy (OR, 1.2; 95% CI, 1.1-1.3; P<.001 for all). Increasing use of HFRT was concentrated in hospital-affiliated sites (P=.002 for interaction). Most patients (69%) received systemic therapy with no differences by site of care (P=.12). Systemic therapy utilization increased (67% in 2015 to 71% in 2019; OR, 1.1 per year; 95% CI, 1.0-1.1) and was less likely for older patients, patients who died within 90 days of RT planning initiation, those who received conventional external-beam RT, and those who received HFRT. HFRT significantly reduced spending compared with LCRT (adjusted β for LCRT = +$8,649; 95% CI, $8,544-$8,755), whereas spending modestly increased with systemic therapy (adjusted β for systemic therapy = +$270; 95% CI, $176-$365). CONCLUSIONS:Although most Medicare beneficiaries received LCRT for primary brain tumors, HFRT utilization increased in hospital-affiliated centers. Despite high-level evidence for elderly patients, discrepancy in HFRT implementation by site of care persists. Further investigation is needed to understand why patients with short survival may still receive LCRT, because this has major quality-of-life and Medicare spending implications.

For patients with central nervous system (CNS) malignancies, liquid biopsies of the cerebrospinal fluid (CSF) may offer an unparalleled source of information about the tumor, with much less risk than traditional biopsies. Two techniques have been adapted to CSF in clinical settings: circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA). CTCs have been employed mostly as a diagnostic tool for leptomeningeal metastases in epithelial tumors, although they may also have value in the prognostication and monitoring of this disease. The ctDNA technology has been studied in a variety of primary and metastatic brain and spinal cord tumors, where it can be used for diagnosis and molecular classification, with some work suggesting that it may also be useful for longitudinal tracking of tumor evolution or as a marker of residual disease. This review summarizes recent publications on the use of these two tests in CSF, focusing on their established and potential clinical applications.

The emergence of liquid biopsy technologies holds great promise in the cancer setting, including in pediatric central nervous system (CNS) tumors. In contrast to broad lower-depth sequencing, commonly referred to as low pass whole genome sequencing (WGS), targeted platforms with a higher depth of coverage have also been established. Here, we review targeted liquid biopsy techniques with applicability to pediatric CNS tumors. These include polymerase chain reaction (PCR), both droplet digital PCR and reverse transcription-based PCR, Sanger sequencing, and next-generation sequencing approaches that incorporate amplicon- and hybrid capture-based methods. The goal of this paper is to facilitate an understanding of these targeted techniques and provide a context for clinical relevance within disease categories, as well as a discussion on optimizing real-world implementation for pediatric CNS tumors.

Malignancies involving the central nervous system present unique challenges for diagnosis and monitoring due to the difficulties and risks of direct biopsies and the low specificity and/or sensitivity of other techniques for assessment. In recent years, liquid biopsy of the cerebrospinal fluid (CSF) has emerged as a convenient alternative that combines minimal invasiveness with the ability to detect disease-defining or therapeutically actionable genetic alterations from circulating tumor DNA (ctDNA). Since CSF can be obtained by lumbar puncture, or an established ventricular access device at multiple time points, ctDNA analysis enables initial molecular characterization and longitudinal monitoring throughout a patient's disease course, promoting optimization of treatment regimens. This review outlines some of the key aspects of ctDNA from CSF as a highly suitable approach for clinical assessment, the benefits and drawbacks, testing methods, as well as potential future advancements in this field. We anticipate wider adoption of this practice as technologies and pipelines improve and envisage significant improvements for cancer care.

PURPOSE:Assessing the risk of common, complex diseases requires consideration of clinical risk factors as well as monogenic and polygenic risks, which in turn may be reflected in family history. Returning risks to individuals and providers may influence preventive care or use of prophylactic therapies for those individuals at high genetic risk. METHODS:To enable integrated genetic risk assessment, the eMERGE (electronic MEdical Records and GEnomics) network is enrolling 25,000 diverse individuals in a prospective cohort study across 10 sites. The network developed methods to return cross-ancestry polygenic risk scores, monogenic risks, family history, and clinical risk assessments via a genome-informed risk assessment (GIRA) report and will assess uptake of care recommendations after return of results. RESULTS:GIRAs include summary care recommendations for 11 conditions, education pages, and clinical laboratory reports. The return of high-risk GIRA to individuals and providers includes guidelines for care and lifestyle recommendations. Assembling the GIRA required infrastructure and workflows for ingesting and presenting content from multiple sources. Recruitment began in February 2022. CONCLUSION:Return of a novel report for communicating monogenic, polygenic, and family history-based risk factors will inform the benefits of integrated genetic risk assessment for routine health care.

PURPOSE:Proton craniospinal irradiation (pCSI) is a promising treatment for patients with solid tumor leptomeningeal metastasis (LM). We hypothesize that genetic characteristics before and changes resulting after pCSI will reflect clinical response to pCSI. We analyzed the cerebrospinal fluid (CSF) circulating tumor DNA (ctDNA) from patients receiving pCSI for LM and explored genetic variations associated with response. EXPERIMENTAL DESIGN:We subjected CSF from 14 patients with LM before and after pCSI to cell-free DNA sequencing using a targeted-sequencing panel. In parallel, plasma ctDNA and primary tumors were subjected to targeted sequencing. Variant allele frequency (VAF) and cancer cell fraction (CCF) were calculated; clonality of observed mutations was determined. Kaplan-Meier analysis was used to associate genomic changes with survival. RESULTS:The median overall survival (OS) for the cohort was 9 months [interquartile range (IQR), 5-21 months]. We showed clonal evolution between tumor and ctDNA of the CSF and plasma with unique mutations identified by compartment. Higher CSF ctDNA mean VAF before pCSI (VAFpre) had worse OS (6 months for VAFpre ≥ 0.32 vs. 9 months for VAFpre < 0.32; P = 0.05). Similarly, increased VAF after pCSI portended worse survival (6 vs. 18 months; P = 0.008). Higher mean CCF of subclonal mutations appearing after pCSI was associated with worse OS (8 vs. 17 months; P = 0.05). CONCLUSIONS:In patients with solid tumor LM undergoing pCSI, we found unique genomic profiles associated with pCSI through CSF ctDNA analyses. Patients with reduced genomic diversity within the leptomeningeal compartment demonstrated improved OS after pCSI suggesting that CSF ctDNA analysis may have use in predicting pCSI response.