mTHPC-mediated photodynamic diagnosis of malignant brain tumors

Radical tumor resection is the basis for the prolonged survival of patients suffering from malignant brain tumors such as glioblastoma multiforme. We have carried out a phase-II study involving 22 patients with malignant brai n tumors to assess the feasibility and the effectiveness of the combination of intraoperative photodynamic diagnosis and fluorescence-guided resection (FGR) mediated by the second-generation photosensitizer meta-tetrahydroxyp henylchlorin (mTHPC). In addition, intraoperative photodynamic therapy (PDT ) was performed. Several commercially available fluorescence diagnostic sys tems were investigated for their applicability in clinical practice. We hav e adapted and optimized a diagnostic system that includes a surgical micros cope, an excitation light source (filtered to 370-440 nm), a video camera d etection system and a spectrometer for clear identification of the mTHPC fl uorescence emission at 652 nm. Especially in regions of faint fluorescence, it turned out to be essential to maximize the spectral information by opti mizing and matching the spectral properties of all components, such as exci tation source, camera and color filters. To sum up, on the basis of 138 tis sue samples derived from 22 tumor specimens, we have been able to achieve a sensitivity of 87.9% and a specificity of 95.7%. This study demonstrates t hat mTHPC-mediated intraoperative FGR followed by PDT is a highly promising concept in improving the radicality of tumor resection combined with a the rapeutic approach.