Systemic vs local administration of delta-aminolevulinic acid for laparoscopic fluorescence diagnosis of malignant intra-abdominal tumors. Experimental study.

BACKGROUND: Administration of delta-aminolevulinic acid (ALA) either systemically or locally results in tumor-specific accumulation of protoporphyrin IX (PpIX). When excited with light at a defined wavelength and viewed with the appropriate filter cells containing PpIX, have a characteristic red fluorescence. We evaluated both locally (intraperitoneally [i.p.]) and systemically (intravenously [i.v.]) administered ALA to compare its effectiveness for laparoscopic fluorescent visualization of intraperitoneal tumors.
METHODS: Peritoneal carcinosis was induced in rats using colon carcinoma cells (CC531). Photosensitization was achieved either by intravenous (i.v. group) or intraperitoneal (i.p. group) application of ALA solution. Staging laparoscopy was performed in both groups, first using conventional white light and subsequently using blue light (380-440 nm) to excite PpIX-induced fluorescence.
RESULTS: Conventional white light laparoscopy showed 142 visible intraperitoneal tumor foci in the i.p. group and 116 such foci in the i.v. group. In the i.p. group, all tumors (100%) also were fluorescence positive, whereas in the i.v. group only 32 of the tumors (28%) showed the typical red fluorescence. In the i.p. group, 30 additional tumors were detected by fluorescence excitation (21%), as compared with eight additional tumors in the i.v. group (7%).
CONCLUSIONS: Fluorescence laparoscopy after local (i.p.) photosensitization with ALA is a more reliable and effective method than systemic (i.v.) photosensitization for the detection of small or occult i.p. tumors.