Effect of photodynamic therapy on urinary bladder function: an experimental study with rats

Photodynamic therapy (PDT) produces localized necrosis with light after pri or administration of a photosensitizing drug. The problems with laser light dosimetry and complications relating to bladder function appear to be impo rtant limiting factors of PDT in urology. Photodynamic therapy on urinary b ladder with normal epithelium of rats was performed using an argon ion lase r as an energy source, with aminolevulinic acid (ALA)-induced protoporphyri n IX (PpIX) photosensitizer. Four hours after ALA intravenous administratio n, the bladders were intravesically radiated with light doses 20, 40, or 80 J/cm(2). Animals in the control group did not receive ALA and were radiate d with 20 J/cm(2) light dose. Three weeks prior to PDT, the bladder capacit y and pressure changes during filling cystometry were assessed. Cystometric s were repeated 1, 3, 7, or 21 days after laser therapy. The light dose 20 J/cm(2) and 40 J/cm(2) together with the used ALA dose caused no reduction in bladder capacity, whereas 80 J/cm(2) light dose produced up to 50% reduc tion in the capacity at 3 weeks postoperatively. In control group without A LA, the animals did not regain more than 34% of the capacity of their contr ol values at 3 weeks. The light dose of 20 J/cm(2) and 40 J/cm(2) with ALA induced functional changes that subsided after day 1. Our results indicate that with proper dosing of photosensitizing drug and light energy, the func tional impairment of urinary bladder may be reduced as transient. These fin dings support the use of PDT as safe therapy of superficial bladder cancer.