The standard of care for treatment of glioblastoma results in a mean survival of only 12 to 15 months. Convection-enhanced delivery (CED) is an investigational therapy to treat glioblastoma that utilizes locoregional drug delivery via a small-caliber catheter placed into the brain parenchyma. Clinical trials have failed to reach their endpoints due to an inability of standard catheters to fully saturate the entire brain tumor and its margins. In this study, we examine the effects of controlled catheter movement on dye dispersal volume in agarose gel brain tissue phantoms. Four different catheter movement control protocols (stationary, continuous retraction, continuous insertion, and intermittent insertion) were applied for a single-port stepped catheter capable of intrainfusion movement. Infusions of indigo carmine dye into agarose gel brain tissue phantoms were conducted during the controlled catheter movement. The dispersal volume (Vd), forward dispersal volume (Vdf), infusion radius, backflow distance, and forward flow distance were quantified for each catheter movement protocol using optical images recorded throughout the experiment. Vd and Vdf for the retraction and intermittent insertion groups were significantly higher than the stationary group. The stationary group had a small but significantly larger infusion radius than either the retracting or the intermittent insertion groups. The stationary group had a greater backflow distance and lower forward flow distance than either the retraction or the intermittent insertion groups. Continuous retraction of catheters during CED treatments can result in larger Vd than traditional stationary catheters, which may be useful for improving the outcomes of CED treatment of glioblastoma. However, catheter design will be crucial in preventing backflow of infusate up the needle tract, which could significantly alter both the Vd and shape of the infusion.
The blood-brain barrier (BBB) presents a formidable obstacle to the effective delivery of systemically administered pharmacological agents to the brain, with ~5% of candidate drugs capable of effectively penetrating the BBB. A variety of biomaterials and therapeutic delivery devices have recently been developed that facilitate drug delivery to the brain. These technologies have addressed many of the limitations imposed by the BBB by: (1) designing or modifying the physiochemical properties of therapeutic compounds to allow for transport across the BBB; (2) bypassing the BBB by administration of drugs via alternative routes; and (3) transiently disrupting the BBB (BBBD) using biophysical therapies. Here we specifically review colloidal drug carrier delivery systems, intranasal, intrathecal, and direct interstitial drug delivery methods, focused ultrasound BBBD, and pulsed electrical field induced BBBD, as well as the key features of BBB structure and function that are the mechanistic targets of these approaches. Each of these drug delivery technologies are illustrated in the context of their potential clinical applications and limitations in companion animals with naturally occurring intracranial diseases.
Standard treatment for glioblastoma is non-curative and only partially effective. Convection enhanced delivery (CED) was developed as an alternative approach for effective loco-regional delivery of drug via a small catheter inserted into the diseased brain. However, previous CED clinical trials revealed the need for improved catheters for controlled and satisfactory distribution of therapeutics. In this study, the arborizing catheter, consisting of six infusion ports, was compared to a reflux-preventing single-port catheter. Infusions of iohexol at a flow rate of 1µL/min/microneedle were performed, using the arborizing catheter on one hemisphere and a single-port catheter on the contralateral hemisphere of excised pig brains. The volume dispersed (Vd) of the contrast agent was quantified for each catheter. Vd for the arborizing catheter was significantly higher than for the single-port catheter, 2235.8 ± 569.7 mm3 and 382.2 ± 243.0 mm3, respectively (n = 7). Minimal reflux was observed, however high Vd values were achieved with the arborizing catheter. With simultaneous infusion using multiple ports of the arborizing catheter, high Vd were achieved at a low infusion rate. Thus, the arborizing catheter promises a highly desirable large volume of distribution of drugs delivered to the brain for the purpose of treating brain tumors.
Glioblastoma has a 5 year survival of only 5.5% and a median patient survival of 12 to 15 months even with gold standard treatment. One potential method of improving treatment of glioblastoma is the use of convection-enhanced delivery (CED) which utilizes local delivery of therapeutics to the brain. However, clinical trials have shown an inability of standard catheters to deliver therapeutics to the entire target area. In this study, we explore the potential of controlled catheter movement to increase the volume dispersed (Vd) of indigo carmine dye in agarose gel brain tissue phantoms. We use four catheter control protocols: stationary, continuous retraction, continuous insertion, and intermittent insertion using a single port stepped catheter. The continuous retraction group resulted in consistent catheter clogging caused by the continued insertion of the catheter and therefore was removed from further analysis. Vd and backflow distance was quantified for all other catheter movement protocols using optical images captured throughout the infusion. Catheter retraction resulted in an increase in Vd of 51% while intermittent insertion resulted in a Vd increase of 24% compared to the stationary catheter. Additionally, a 37% reduction in backflow distance was seen with the retracting catheter when compared to the stationary catheter. These results are further supported by a simplified computational model that we have created. The computational model simulates the infusion of indigo carmine dye through an agarose gel brain tissue phantom and shows an increase in Vd of over 100% with catheter retraction. The increased Vd and decreased backflow distance afforded by the retracting catheter, suggests that the use of catheter movement may be a useful technique in increasing drug dispersal in tumorous tissue. Additional work in live and excised tissue should be conducted to confirm these results and an exploration of optimal needle movement protocols is necessary.
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