Photodynamic treatment of cholesteatoma of the ear induced experimentally in rabbits: preliminary report

Abstract In a previous project on haematoporphyrin (HP) uptake by experimentally induced cholesteatoma of the rabbit, it was shown that HP concentration was remarkably high in the cholesteatoma, with a peak at three hours after intravenous administration of the drug. On the basis of these results an attempt was made to destroy the matrix of cholesteatoma by means of photodynamic therapy. Cholesteatomas were induced bilaterally in the ears of eight rabbits which were divided into two groups, according to the interval between HP administration (5 mg/kg body weight) and irradiation. The irradiation was carried out with light at 600–680 nm, filtered from the emission a quartz halogen lamp (dose rate 300 mW cm–2; total dose 120 J cm–2). The first group was submitted to photodynamic therapy after three hours and the second after twelve hours. In both groups half the rabbits were sacrificed at 24 h and half at 48 h post-irradiation. Histological studies showed significant vascular lesions, necrosis of the wall of the cholesteatoma, interstitial extravasation of blood, and oedema in a high percentage of the animals. The lesions were much greater in animals sacrificed at 48 h after photodynamic therapy.