The 100 Most-Cited Articles About Convection-Enhanced Delivery to the Brain: A Bibliometric Analysis

A phase I study of convection-enhanced delivery (CED) of liposomal-irinotecan using real-time magnetic resonance imaging in patients with recurrent high-grade glioma

BACKGROUND

Irinotecan demonstrates anti-tumor efficacy in preclinical glioma models but clinical results are modest due to drug delivery limitations. Convection enhanced delivery (CED) improves drug delivery by increasing intratumoral drug concentration. Real-time magnetic resonance imaging of infusate delivery during CED may optimize tumor coverage. This phase 1 trial examines the safety and tolerability of liposomal irinotecan and gadolinium delivered via CED using real-time MRI guidance in recurrent high-grade glioma patients.

METHODS

Initially, a 3 + 3 dose-escalating, single dose trial was planned with 4 cohorts based on a fixed drug dose and volume. After 9 patients, a protocol amendment allowed for variable volume and dose of the study agent based on tumor size. The amended design specified 'personalized' drug volume but fixed concentration of 20 mg/mL of liposomal irinotecan in the first cohort escalating to 40 mg/mL in the second cohort.

RESULTS

Eighteen patients with recurrent WHO grade 3 or 4 gliomas (diameter 1-4 cm) were treated. Based on the tumor volume, the total dose of liposomal irinotecan was 20-680 mg in a total volume of 2-17 ml. Technical challenges were overcome by real-time MRI guidance and protocol amendment. The only dose-limiting toxicity (DLT) was a grade 3 stroke. Safety and survival information is presented.

CONCLUSIONS

CED of liposomal irinotecan using real-time MRI in patients with recurrent high-grade glioma is feasible. Image-guidance allowed for improved placement of CED cannulas and optimal tumor coverage. Our results warrant further study with repeat CED dosing.

Convection-enhanced delivery for H3K27M diffuse midline glioma: how can we efficaciously modulate the blood-brain barrier?

Graphical abstract [Formula: see text].

Evaluating infusate parameters for direct drug delivery to the brainstem: a comparative study of convection-enhanced delivery versus osmotic pump delivery

OBJECTIVE

Convection-enhanced delivery (CED) and osmotic pump delivery both have been promoted as promising techniques to deliver drugs to pediatric diffuse intrinsic pontine gliomas (DIPGs). Correspondingly, the aim of this study was to understand how infusate molecular weight (MW), duration of delivery, and mechanism of delivery (CED or osmotic pump) affect volume of distribution (Vd) in the brainstem, to better inform drug selection and delivery in future DIPG investigations.

METHODS

A series of in vivo experiments were conducted using rat models. CED and osmotic pump delivery systems were surgically implanted in the brainstem, and different MW fluorescent dextran beads were infused either once (acute) or daily for 5 days (chronic) in a volume infused (Vi). Brainstems were harvested after the last infusion, and Vd was quantified using serial sectioning and fluorescence imaging.

RESULTS

Fluorescence imaging showed infusate uptake within the brainstem for both systems without complication. A significant inverse relationship was observed between infusate MW and Vd in all settings, which was distinctly exponential in nature in the setting of acute delivery across the 570-Da to 150-kDa range. Chronic duration and CED technique resulted in significantly greater Vd compared to acute duration or osmotic pump delivery, respectively. When accounting for Vi, acute infusion yielded significantly greater Vd/Vi than chronic infusion. The distribution in CED versus osmotic pump delivery was significantly affected by infusate MW at higher weights.

CONCLUSIONS

Here the authors demonstrate that infusate MW, duration of infusion, and infusion mechanism all impact the Vd of an infused agent and should be considered when selecting drugs and infusion parameters for novel investigations to treat DIPGs.

Bypassing the Blood-Brain Barrier: Direct Intracranial Drug Delivery in Epilepsies

Epilepsies are common chronic neurological diseases characterized by recurrent unprovoked seizures of central origin. The mainstay of treatment involves symptomatic suppression of seizures with systemically applied antiseizure drugs (ASDs). Systemic pharmacotherapies for epilepsies are facing two main challenges. First, adverse effects from (often life-long) systemic drug treatment are common, and second, about one-third of patients with epilepsy have seizures refractory to systemic pharmacotherapy. Especially the drug resistance in epilepsies remains an unmet clinical need despite the recent introduction of new ASDs. Apart from other hypotheses, epilepsy-induced alterations of the blood-brain barrier (BBB) are thought to prevent ASDs from entering the brain parenchyma in necessary amounts, thereby being involved in causing drug-resistant epilepsy. Although an invasive procedure, bypassing the BBB by targeted intracranial drug delivery is an attractive approach to circumvent BBB-associated drug resistance mechanisms and to lower the risk of systemic and neurologic adverse effects. Additionally, it offers the possibility of reaching higher local drug concentrations in appropriate target regions while minimizing them in other brain or peripheral areas, as well as using otherwise toxic drugs not suitable for systemic administration. In our review, we give an overview of experimental and clinical studies conducted on direct intracranial drug delivery in epilepsies. We also discuss challenges associated with intracranial pharmacotherapy for epilepsies.

Our Efforts in Understanding Normal Pressure Hydrocephalus: Learning from the 100 Most Cited Articles by Bibliometric Analysis

BACKGROUND

Normal pressure hydrocephalus (NPH) is a syndrome that was characterized several decades ago; however, its optimal diagnosis and management remain unclear. Our objective was to evaluate citation and bibliometric characteristics of the 100 most cited articles about NPH to better understand the state of research efforts in the field and where improvements may arise.

METHODS

Elsevier's Scopus database was searched for the 100 most cited articles that focused on NPH. Articles were characterized and various bibliometric parameters were compared. Categorical data were analyzed using Pearson χ², and continuous data were analyzed using either linear regression or a Student t test.

RESULTS

The 100 most cited articles were published between 1965 and 2014, from 16 unique countries in 38 unique journals. The most common outcome types of these articles were clinical (n = 77). Median number of citations and rate of citations were 114 citations and 5.9 citations/year since publication, respectively, with a significant inverse linear relationship between the 2 parameters (P < 0.01). The most common year of publication was 2002 (n = 10), and the most common country of origin was the United States (n = 40). Higher citation rates were associated with more recent articles (P < 0.01) and more authors (P < 0.01).

CONCLUSIONS

In the 100 most cited articles about NPH, there has been a distinct shift toward a more globalized effort in recent decades. The lack of more impactful articles in recent decades highlights that particular classic studies still penetrate practice and the possible need to reconsider our contemporary views on NPH to further advance the field.