ALA (5-aminolevulinic acid)-induced protoporphyrin IX fluorescence in the endoscopic diagnostic and control of pharyngo-laryngeal cancer

Photodynamic diagnosis is a modern method for the fluorescence imaging of superficial pharyngeal and laryngeal tumours. 5-aminolevulinic acid (ALA)-induced protoporphyrin IX fluorescence benefits the tumour selective accumulation of protoporphyrin; therefore, tumours can be differentiated from healthy tissue. ALA-induced fluorescence of laryngo-pharyngeal tumours and precancerous and benign lesions were evaluated by endoscopy. At the Department of Otorhinolaryngology, Head and Neck Surgery, Szeged, Hungary, 31 patients underwent ALA-induced protoporphyrin fluorescence imaging. After topical application of ALA, mesopharyngeal tumours were visualised by direct fluorescence endoscopy. Laryngeal and hypopharyngeal tumours were examined with a laryngomicroscope with the patients under general anaesthesia after inhalation of an ALA solution. Intensity of PPIX fluorescence was classified and compared with pathological findings. The examination of all 13 laryngeal and 12 pharyngeal tumours resulted in a middle or strong intensity of red fluorescence, but for one cancer, four praecancerous and two benign lesions. Healthy tissues showed green autofluorescence. Margins of mesopharyngeal and vocal cord tumours were clearly outlined under fluorescent vision, giving a helpful contribution to diagnosis and therapy even in clinically non-visible tumours. Laryngomicroscopy combined with laser surgery also indicated PPIX fluorescence examination visualising margins of the tumour intermediately with the endoscope. The ALA-induced PPIX fluorescence imaging method revealed a sensitivity of 96%. This method is applicable for detecting early superficial tumours, margins of tumours and follow-up after surgery/radiation therapy in the laryngo-pharynx.