Blood-Brain Barrier Disruption in Neuro-Oncology: Strategies, Failures, and Challenges to Overcome

The blood-brain barrier (BBB) presents a formidable challenge in the development of effective therapeutics in neuro-oncology. This has fueled several decades of efforts to develop strategies for disrupting the BBB, but progress has not been satisfactory. As such, numerous drug- and device-based methods are currently being investigated in humans. Through a focused assessment of completed, active, and pending clinical trials, our first aim in this review is to outline the scientific foundation, successes, and limitations of the BBBD strategies developed to date. Among 35 registered trials relevant to BBBD in neuro-oncology in the ClinicalTrials.gov database, mannitol was the most common drug-based method, followed by RMP-7 and regadenoson. MR-guided focused ultrasound was the most common device-based method, followed by MR-guided laser ablation, ultrasound, and transcranial magnetic stimulation. While most early-phase studies focusing on safety and tolerability have met stated objectives, advanced-phase studies focusing on survival differences and objective tumor response have been limited by heterogeneous populations and tumors, along with a lack of control arms. Based on shared challenges among all methods, our second objective is to discuss strategies for confirmation of BBBD, choice of systemic agent and drug design, alignment of BBBD method with real-world clinical workflow, and consideration of inadvertent toxicity associated with disrupting an evolutionarily-refined barrier. Finally, we conclude with a strategic proposal to approach future studies assessing BBBD.

The Role of Stereotactic Radiosurgery in the Management of Brain Metastases From a Health-Economic Perspective: A Systematic Review

BACKGROUND

Stereotactic radiosurgery (SRS) is an effective option in the management of brain metastases, offering improved overall survival to whole-brain radiation therapy (WBRT). However, given the need for active surveillance and the possibility of repeated interventions for local/distant brain recurrences, the balance between clinical benefit and economic impact must be evaluated.

OBJECTIVE

To conduct a systematic review of health-economic analyses of SRS for brain metastases, compared with other existing intervention options, to determine the cost-effectiveness of this treatment across different clinical scenarios.

METHODS

The MEDLINE, EMBASE, Cochrane, CRD, and EconLit databases were searched for health-economic analyses, according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, using terms relevant to brain metastases and radiation-based therapies. Simple cost analysis studies were excluded. Quality analysis was based on BMJ Consolidated Health Economics Reporting Standards (CHEERS) checklist.

RESULTS

Eleven eligible studies were identified. For lesions with limited mass effect, SRS was more cost-effective than surgical resection (6 studies). In patients with Karnofsky performance scale (KPS) >70 and good predicted survival, SRS was cost-effective compared to WBRT (7 studies); WBRT became cost-effective with poor performance status or low anticipated life span. Following SRS, routine magnetic resonance imaging surveillance saved $1326/patient compared to symptomatic imaging due to reduced surgical salvage and hospital stay (1 study).

CONCLUSION

Based on our findings, SRS is cost-effective in the management of brain metastases, particularly in high-functioning patients with longer expected survival. However, before an optimal care pathway can be proposed, emerging factors such as tumor molecular subtype, diagnosis-specific graded prognostic assessment, neuroprognostic score, tailored surveillance imaging, and patient utilities need to be studied in greater detail.

Comparing Effects of Treatment: Controlling for Confounding

BACKGROUND

Determining true causal links between an intervention and an outcome forms an imperative task in research studies in neurosurgery. Although the study results sometimes demonstrate clear statistical associations, it is important to ensure that this represents a true causal link. A confounding variable, or confounder, affects the association between a potential predictor and an outcome.

OBJECTIVE

To discuss what confounding is and the means by which it can be eliminated or controlled.

METHODS

We identified neurosurgical research studies demonstrating the principles of eliminating confounding by means of study design and data analysis.

RESULTS

In this report, we outline the role of confounding in neurosurgical studies after giving an overview of its identification. We report on the definition of confounding and effect modification, and the differences in the 2. We explain study design techniques to eliminate confounding, including simple, block, stratified, and minimization randomization, along with restriction of sample and matching. Data analysis techniques of eliminating confounding include regression analysis, propensity scoring, and subgroup analysis.

CONCLUSION

Understanding confounding is important for conducting a good research study. Study design techniques provide the best way to control for confounders, but when not possible to alter study design, data analysis techniques can also provide an effective control.

The Effect of Older Age on the Perioperative Outcomes of Spinal Fusion Surgery in Patients With Lumbar Degenerative Disc Disease With Spondylolisthesis: A Propensity Score-Matched Analysis

BACKGROUND

Degenerative spondylolisthesis (DS) is often treated with lumbar spinal fusion (LSF). However, there is concern that the morbidity of LSF may be prohibitively high in older adults.

OBJECTIVE

To evaluate the impact of advanced age on the safety of LSF for DS.

METHODS

Patients who underwent LSF for DS were retrospectively identified from National Surgical Quality Improvement Program datasets for 2011 to 2015 using Current Procedural Terminology codes. Data on demographic characteristics, comorbidities, surgical factors, and 30-d morbidity and mortality were collected. Propensity score matching (nearest neighbor) was performed with age (<70 vs ≥70 yr) as the dependent variable and sex, type of fusion procedure, number of levels fused, diabetes, smoking, hypertension, and chronic steroid use as covariates. Outcomes were compared between age <70 and ≥70 groups.

RESULTS

The study cohort consisted of 2238 patients (n = 1119, age <70; n = 1119, age ≥70). The 2 age groups were balanced for key covariates including sex, race, diabetes, hypertension, CHF, smoking, chronic steroid use, type of fusion, and number of levels. Rates of all complications were similar between younger and older age groups, except urinary tract infection, which was more frequent among the ≥70 age group (OR 2.32, P = .009). Further, patients in the older age group were more likely to be discharged to a rehabilitation (OR 2.94, P < .001) or skilled care (OR 3.66, P < .001) facility, rather than directly home (OR 0.25, P < .001).

CONCLUSION

LSF may be performed safely in older adults with DS. Our results suggest older age alone should not exclude a patient from undergoing lumbar fusion for DS.

Medical and socioeconomic predictors of quality of life in myelomeningocele patients with shunted hydrocephalus

INTRODUCTION

Children with myelomeningocele (MMC) often develop hydrocephalus, and the combination of these conditions can lead to psychosocial, cognitive, and physical health issues that decrease their health-related quality of life (HRQOL). The goal of the present study was to understand the QOL in patients with MMC and shunted hydrocephalus.

METHODS

Data from the Toronto Hydrocephalus QOL Database was acquired between 2004 and 2009 using parent-completed questionnaires and, when appropriate, child-completed questionnaires: Hydrocephalus Outcome Questionnaire (HOQ) and the Health Utilities Index. We identified several medical and socioeconomic factors potentially relevant to the outcome measure (e.g., level of myelomeningocele, length of stay in hospital, and shunt-related hospital admissions; family functioning, income, parental education, employment status, etc.). Linear regression models were used to examine associations between potential predictor variables and HRQOL, with P < 0.05 in the multivariate model suggesting significance.

RESULTS

The analysis consisted of 131 patients (mean age = 12.6, SD = 3.7). The mean HUI score was 0.51, and the mean HOQ overall health score was 0.67. There was a significant association between lower age and higher HOQ social-emotional health (P = 0.03) and HUI scores (P = 0.03), lower anatomical level of myelomeningocele and higher HUI scores (P = 0.01), better family functioning and higher HOQ overall health scores (P = 0.004), and higher family income and higher HOQ overall health, physical health, and HUI scores (P = 0.001, P = 0.003, and P = 0.02, respectively).

CONCLUSION

Myelomeningocele patients with shunted hydrocephalus can have a poor health-related quality of life. Our results indicate a strong association of income and family functioning on quality of life, along with younger age and lower level of myelomeningocele.