SURG-25INTERSTITIAL PHOTODYNAMIC THERAPY OF DE-NOVO GLIOBLASTOMA MULTIFORME WHO IV

Abstract

BACKGROUND: The prognosis of glioblastoma (GBM) still remains dismal. We provide an outcome analysis for selected patients with de-novo GBMs undergoing stereotactic interstitial photodynamic therapy (iPDT). METHODS: iPDT was offered to 15 adult patients with de-novo, small sized (diameter < 4cm), and unresectable supratentorial GBMs; tumors did not infiltrate the midline/basal ganglia or the ventricular system. 5-aminolevulinic acid was used as a photosensitizer (dose: 20 or 30 mg/kg). A 3-D treatment-planning software was used for both calculation of the treatment volume and dosimetric analyses. Accurate positioning of the light diffusers was achieved using stereotactic techniques. Irradiation was performed with a wavelength of 633 nm (median dose: 12.960J). Patients received standard treatment after iPDT (usually radiotherapy plus temozolomide). Outcome after iPDT was compared with a positively selected patient population (n = 112) undergoing complete tumor resection and a complete course of adjuvant treatment according to the EORTC/NCIC protocol. Survival and progression free survival (PFS) were analyzed with the Kaplan Meier method. Informed consent was obtained from all patients. RESULTS: Median follow-up of survivors in the iPDT and resection group was 34 and 37 months. Treatment groups did not differ in terms of age, performance scores and MGMT-promotor methylation. Outcome was significantly better after iPDT (median PFS: 16 vs 10.2 months, p < 0.001. 3-year survival: 56% vs 21%, p<0.01). Six out of15patients of theiPDTgroup experienced long-term progression free survival >30 months (range: 32-68 months). MGMT-promoter methylation status was the strongest prognostic/predictive factor in both groups. Transient morbidity was seen in 7/15 iPDT patients (transient aphasia, pulmonary embolism). CONCLUSIONS: Observed longterm PFS after iPDT points to the induction of so far unknown tumor controlling processes possibly overcoming limitations of conventional treatment concepts. Further understanding of the underlying mechanisms might help to identify patients most suitable for iPDT.