Sensitization and photodynamic therapy (PDT) of gastrointestinal tumors with 5-aminolaevulinic acid (ALA) induced protoporphyrin IX (PPIX). A pilot study.

5-Aminolaevulinic acid (ALA) is a promising agent for photodynamic therapy (PDT) sensitization as it can be given orally and only causes skin photosensitivity for 1-2 days. In fluorescence and photodynamic studies 26 patients with benign and malignant gastrointestinal tumors were given 30-60 mg ALA orally (single or divided doses) and biopsies were taken of tumor and normal tissue at 1-24 hours for fluorescence microscopy. With 30 mg/kg, highest protoporphyrin IX (PPIX) levels were seen in esophagus, duodenum and less in colon, but without tumor selectivity. Better tumor selectivity was seen in colon after 60 mg/kg (5:1). Six patients had transient rises in transaminases and five mild nausea. Sixteen patients were later treated (after further ALA) with red light (628 nm, bare or diffuser fibre, 50-100 J at 50 mW at each site). All but two showed subsequent necrosis, but only 0.5-1.5 mm of depth. PDT with ALA is simple, safe and promising for tumors in the gastrointestinal tract. Modification of treatment parameters may make it suitable for larger lesions.