Inducing intravesical hyperthermia of the ex-vivo porcine bladder wall: radiofrequency-induction versus recirculation using a custom-made device

Abstract

Introduction: Several techniques can be used to treat intravesical chemohyperthermia (ChHT). We compared radiofrequency-induced hyperthermia (RF-HT) with conductive hyperthermia (C-HT) for their ability to induce bladder wall temperatures of >40.5 °C, the target temperature for ChHT.

Materials and Methods: Fresh porcine bladders (n = 12) were placed in a temperature-controlled saline bath to simulate body temperature and circulation. HT was induced with RF-HT (43 °C) or C-HT (inflow temperature 44 and 46 °C) using a custom-made device. In two additional bladders, we varied intravesical solution and volume. Temperatures were recorded with a three-way catheter containing three mucosal and two urethral thermocouples (TCs) and a 915 MHz RF antenna, and with external TCs in the bladder wall at three different levels and three different locations.

Results: Target temperature (40.5 °C) was reached in the submucosa at all locations by both techniques. In the detrusor, target temperature was reached by RF-HT at the bladder neck and side wall. C-HT₄₆ reached significantly higher submucosal temperatures at the side wall. The bladder dome seemed best heated by C-HT, although a high inflow temperature (46 vs. 44 °C) was required (ns). Intravesical saline resulted in higher temperatures than sterile water for RF-HT. A volume of 100 mL resulted in higher bladder dome temperatures for RF-HT, and higher bladder neck with lower dome temperatures for C-HT.

Conclusion: Our results indicate a slightly superior heating capacity for RF-HT compared to C-HT, whereas for the bladder dome, the reverse seems true. Comparative studies are warranted to evaluate whether HT efficacy differs between both techniques, with emphasis on tumor location.

Keywords:

• Hyperthermia
• temperature
• urinary bladder neoplasms
• radiofrequency/microwave
• short wave therapy

Acknowledgements

We would like to thank Gerard van Ooijen for his technical support with the thermocouples, and Alex Hanssen for his support during the implementation of the experiment.

Catheters for this study were donated by Medical Enterprises Ltd. (MEL). The Synergo® system was provided by MEL. No further sponsoring was received.

Disclosure statement

J. Alfred Witjes is an Advisor for Sanofi Pasteur, Spectrum, Astellas (not related to this manuscript); is an Advisor for Medical Enterprises Ltd. (Synergo®); has no associated financial interest or conflict of interest. No potential conflict of interest was reported by the remaining authors.

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.