title: Simulation of intratumoral release of Etanidazole: effects of the size of surgical opening.
abstract: The efficacy of radiotherapy can be enhanced by the delivery of radiosensitizer (Etanidazole) to brain tumor from biodegradable polymer implants. This process is investigated by simulation carried out at a cut section of tumor with polymeric wafers of Etanidazole loading implanted in the resected cavity. The coupled mass and momentum equations are solved to obtain the transient solution of the drug distribution in the tumor. The polymeric delivery shows high therapeutic index, indicating the wafers' success in delivering more drugs to the tumor rather than to the tissue. The penetration distance of Etanidazole was found to decrease from 14 mm (at 5th/40th day after implantation) to 6.5 mm (at 30th/75th day), suggesting an initial high burst of drug release which cause nearby tissue toxicity and a low effective drug delivery towards the later stages. The short penetration depth is due to Etanidazole having low interstitial Peclet number and high elimination/diffusion modulus. Edema causes the interstitial pressure, velocity, and concentration to increase in all domains, and leads to enhanced convection and a lowering of therapeutic index. Simulations on the open tumor geometry show significantly lower efficacy of the drug delivery due to the uneven distribution of drug in the tumor zone.
authors.affiliation: Department of Chemical and Environmental Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576.
authors.forename: Wilson Hor Keong
authors.initials: WH
authors.lastname: Tan
authors.forename: Timothy
authors.initials: T
authors.lastname: Lee
authors.forename: Chi-Hwa
authors.initials: CH
authors.lastname: Wang
mesh_terms: D001682:Biological Availability; D001932:Brain Neoplasms / Q000378:metabolism / Q000601:surgery*; D003198:Computer Simulation; D016503:Drug Delivery Systems; D004487:Edema / Q000209:etiology; D017341:Etanidazole / Q000008:administration & dosage* / Q000378:metabolism / Q000493:pharmacokinetics; D045604:Extracellular Fluid; D006801:Humans; D015918:Infusion Pumps, Implantable; D008433:Mathematics; D008954:Models, Biological; D019635:Neurosurgical Procedures / Q000009:adverse effects; D011838:Radiation-Sensitizing Agents / Q000008:administration & dosage* / Q000378:metabolism / Q000493:pharmacokinetics
chemical_list: D011838:Radiation-Sensitizing Agents; D017341:Etanidazole