Fluorescence guided resection for malignant glioma using 5-aminolevulinic acid

Background: Oral application of 20 mg/kg body weight of 5-aminolevulinic acid (ALA) results in a highly specific accumulation of fluorescent Protoporphyrin IX (PpIX) in malignant glioma tissue. In a clinical phase II study, Photodynamic Therapy (PDT) to postsurgical tumor-remnants was monitored by fluorescence spectroscopy and photobleaching of PpIX was detected. Methods: Fluorescence spectra were measured from the tumor remnant pre and at intervals during PDT with 100, 150 and 200 J/cm(2) and from adjacent normal cortex. The spectra obtained were fitted with spectra from pure PpIX, autofluorescence and photoproducts, the fit-parameters quantifying the contributions of these components to the measured spectrum. Results: The PpIX-fluorescence bleached to 8%, 16% and 1% of the initial intensity for the 100, 150 and 200 J/cm(2)-groups (median values). Photoproduct formation was minimal. PpIX-fluorescence of normal cortex was 6% of tumor remnant fluorescence (median, range: 0% to 49%).