Photodynamic management of bladder cancer

Abstract

Bladder cancer (BC) is among the most expensive oncological diseases. Any improvement in diagnosis or therapy carries a high potential for reducing costs. Fluorescence cystoscopy relies on a selective formation of Protoporphyrin IX (PpIX) or more general photoactive porphyrins (PAP) in malignant urothelium upon instillation of 5-aminolevulinic acid (5-ALA) or its hexyl-derivative h-ALA. Fluorescence cystoscopy equipment has been developed with the aim to compensate for the undesired distortion caused by the tissue optical properties by displaying the red fluorescence simultaneously with the backscattered blue light. Many clinical studies proved a high sensitivity in detecting flat carcinoma in situ and small papillary malignant tumours. As a result, recurrence rates were significantly decreased in most studies. The limitation lies in a low specificity, caused by false positive findings at inflamed bladder wall. Optical coherence tomography (OCT) is currently being investigated as a promising tool to overcome this limitation. H-ALA-PDT (8 or 16 mM h-ALA in 50 ml instillation for 1-2 h, white light source, catheter applicator) has recently been investigated in a phase I study. 17 patients were applied 100 J/cm2 (3 patients received incrementing doses of 25 - 50 - 100 J/cm2) during approx. 1 hour irradiation time in 3 sessions, 6 weeks apart. PDT was performed without any technical complications. Complete photobleaching of the PpIX-fluorescence, as intended, could be achieved in 43 of 45 PDT-sessions receiving 100 J/cm2. The most prominent side effects were postoperative urgency and bladder pain, all symptoms being more severe after 16 mM h-ALA. Preliminary evaluation shows complete response assessed at 3 months after the third PDT-session (i.e. 6 months after first treatment) in 9 of 12 patients. 2 of these patients were free of recurrence until final follow-up at 84 weeks.