Nanoparticle-enhanced transurethral microwave therapy shows promise for BPH

New York-Nanoparticle technology shows promise for improving the tissue-ablating efficiency of transurethral microwave therapy (TUMT) for treating BPH, according to recently reported preclinical data.

Pretreatment injection of iron oxide (Fe₃O₄) nanoparticles resulted in immediate response to microwave energy, higher temperature at a given energy level, and at least equivalent tissue necrosis compared with conventional TUMT.

"Use of nanoparticles as heating adjuncts can potentially increase the effectiveness of TUMT systems," said first author Richard Lee, MD, a clinical and research fellow in urology at Weill Medical College at Cornell University in New York, working with Alexis Te, MD, and colleagues.

Advances in nanoparticle design have led to development of particles that respond to microwave energy, creating the potential for their use as a thermal adjunct, Dr. Lee explained at the AUA annual meeting in San Francisco. Control of particle size, shape, and material composition influences the response to microwave energy.

Nanoparticles raise temperature

The current study utilized 5-nm Fe₃O₄ nanoparticles encapsulated in a polyethylene glycol shell that were designed to provide optimal response to 915-MHz microwave energy. In vitro studies showed that adding the particles to water resulted in a 10° C higher temperature compared with water alone when heated with a commercial microwave oven operating at 50% of maximum power. The temperature response of the nanoparticles scaled to concentration such that higher concentrations achieved greater temperature response in the in vitro studies.

Studies involving an ex vivo model showed that injection of the nanoparticles into discrete areas of a cadaveric bull prostate led to a 7.5° C higher temperature compared with control areas after application of 915 MHz of microwave energy through a TUMT catheter.

Similarly, in vivo studies involving a canine model showed that application of microwave energy led to immediate temperature response to microwave power variations on the side of the prostate injected with the nanoparticles compared to only a gradual increase in the uninjected contralateral side. The temperature difference reached a maximum of 15° C.

"We see a potential opportunity to achieve equivalent tissue necrosis effects with less power compared with conventional TUMT and to potentially incur fewer side effects," Dr. Lee said.

Future steps in the evaluation of nanoparticles include a "tuning" process to identify the optimal parameters for use with TUMT and possibly an exploration of methods to improve nanoparticle targeting to enhance tissue specificity, he added.

Dr. Te disclosed financial or other relationship with GlaxoSmithKline and American Medical Systems.