Development and pre-clinical test of a phosphorous-32 containing polyetheretherketone foil aiming at urethral stricture prevention by low-dose-rate brachytherapy

Purpose
Primary or recurrent urethral stenoses are common clinical problems. The aim of this feasibility study was development and application test of a novel radioactive catheter for potential use in low-dose-rate (LDR) brachytherapy to prevent urethral stenosis.

Material and methods
A beta radiation emitting phosphorous-32 (32P)-foil was developed and integrated in indwelling catheter, which is usually inserted after surgical intervention in the urethra. Activity and dose distribution were measured after neutron activation of the phosphorus-31 (31P)-foil component with scintillation techniques as well as radiochromic films, and compared to MC simulations. Practicability and radiation safety of this new applicator were tested on male rabbits, which, before catheter application, had undergone a new method of stricture induction by radial laser light irradiation.

Results
Measured dose distributions of catheters with 32P-foils were found to be in good agreement with MC simulations. Wash-out tests confirmed the radioactive catheter setup to be inside permitted limits of a sealed source. Strictures could be induced by laser light in all animals, surgically treated by slitting and irradiation with a 7-day dose of 15 Gy or 30 Gy, without adverse effects of radiation during a 4-week observation time.

Conclusions
This proof-of-concept study presents a safe and technically simple approach to LDR brachytherapy intending to prevent urethral stenosis. The prescribed irradiation dose can be administered in a reproducible and precise manner using a urethral catheter as a carrier of beta radiating foil. The study duration of 63 days was too short to make statistically significant stricture-related conclusions. This approach may be considered for similar problems in other hollow organs and in cases regarding superficial hyper-proliferation.