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Interstitial photodynamic therapy of nonresectable malignant glioma recurrences using 5‐aminolevulinic acid induced protoporphyrin IX
Author(s) -
Beck Tobias J.,
Kreth Friedrich W.,
Beyer Wolfgang,
Mehrkens Jan H.,
Obermeier Andreas,
Stepp Herbert,
Stummer Walter,
Baumgartner Reinhold
Publication year - 2007
Publication title -
lasers in surgery and medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 112
eISSN - 1096-9101
pISSN - 0196-8092
DOI - 10.1002/lsm.20507
Subject(s) - protoporphyrin ix , photodynamic therapy , glioma , nuclear medicine , fluence , materials science , irradiation , optics , chemistry , biomedical engineering , medicine , cancer research , physics , nuclear physics , organic chemistry
Background and Objective Limited knowledge of the light and temperature distribution within the target volume in combination with non‐selective accumulation of the applied photosensitizers (PS) has hampered the clinical relevance of interstitial photodynamic therapy (iPDT) for treatment of malignant glioma patients. The current pilot study focused on the development and the clinical implementation of an accurate and reproducible irradiation scheme for iPDT using 5‐aminolevulinic acid (5‐ALA) induced protoporphyrin IX (PPIX) as a selectively working PS. Study Design/Materials and Methods Monte Carlo simulations of fluence rate and heat transport simulations were performed using the optical properties of normal brain tissue infiltrated by tumor cells (absorption coefficient µ a = 0.2 cm −1 , reduced scattering coefficient: µ ′ s = 20 cm −1 ). A modified 3‐D treatment‐planning software was used to calculate both, the treatment‐volume and the exact position of the light diffusers within the lesion. The feasibility and the risk of iPDT were tested in 10 patients with small and circumscribed recurrent malignant gliomas. Results The optimum distance between the implanted light diffusers was determined to be 9 mm with regard to both fluence rate and temperature distribution. For this distance a temperature increase above 42°C was not expected to occur. Up to six cylindrical light diffusers were stereotactically implanted to achieve a complete irradiation of the tumor volume, which was possible in every single patient (mean tumor volume: 5.9 cm 3 ). The total applied light fluence was between 4,320 J and 11,520 J. Side effects of iPDT were not observed. Median survival was 15 months. Conclusion 5‐ALA iPDT in combination with a 3‐D treatment‐planning (which was based on optical and thermal simulations) is a safe and feasible treatment modality. The clinical impact of these findings deserves further prospective evaluation. Lasers Surg. Med. 39:386–393, 2007. © 2007 Wiley‐Liss, Inc.