Behaviour of haematoporphyrin derivative in adenomas and adenocarcinomas of the colon: a microfluorometric study

Intravenously injected haematoporphyrin derivative localizes in malignant tissue more than it does in the surrounding normal tissues; this allows cancer to be treated photodynamically. The aim of this study is to determine whether adenomas of the large bowel, which are benign precarcinomatous lesions, accumulate HPD as well as does malignant tissue, and whether such accumulation occurs to a greater extent than it does in the surrounding normal mucosa. For this purpose, microspectrofluorometric analysis was performed on biopsy samples of adenomas, on adenocarcinomas, and on normal mucosa, and the data were compared. The samples were obtained from patients affected by histologically proven adenocarcinomas and synchronous adenomas of the bowel 48h after intravenous injection of HPD (3 mg/kg bodyweight), that is, the time interval usually required for photodynamic therapy. The intensity of fluorescence of the adenomas was a little lower than that observed from adenocarcinomas, but was higher than that from the surrounding mucosa. The fluorescence spectra from adenomas and from adenocarcinomas showed three main emission bands centred at about 630, 670 and 700 nm. The relative amplitudes of the band at 630 and 670 nm in benign and malignant colorectal tumours varied with the excitation wavelength, depending on the different physicochemical state of the accumulated drug. A further analysis, performed 72 h after administration, indicated the existence of an intratissue turnover of the porphyrins.