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doi:10.1016/S1095-6433(01)00545-1 
Copyright © 2002 Elsevier Science Inc. All rights reserved.
Tumor P
2 changes during photodynamic therapy depend upon photosensitizer type and time after injection*1
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Brian W. Pogue
, 
, a, Julia A. O'Harab, Isak A. Goodwina, Carmen J. Wilmotb, Gregory P. Fourniera, Altug R. Akaya and Harold Swartzb
Received 10 January 2001;
Abstract
In this study, the vascular and tissue oxygen changes induced by photodynamic therapy in the RIF-1 tumor were examined, using electron paramagnetic resonance (EPR) oximetry. Two photosensitizers, including verteporfin (BPD-MA in a lipid-based formulation) and aminolevulinic acid-induced protoporphyrin IX (ALA-PPIX), were investigated with optical irradiation, sufficient to induce sub-curative damage in the tumor tissue, and the transient changes in P
2 and vascular perfusion were examined. A large increase in tissue oxygenation (from 3 up to 9.5 mmHg) was observed when treated with ALA-PPIX based photodynamic therapy, which lasted during the treatment and a small residual increase that returned back to baseline levels by 48 h after treatment. With verteporfin-based photodynamic therapy, one group of animals was irradiated 15 min after injection and exhibited a small decrease in oxygenation relative to pre-irradiation levels. The second group was irradiated at 3 h after injection and exhibited a large increase in the average P
2, (from 3 to 15 mmHg) by the end of the treatment. These observations indicate that photodynamic therapy significantly increases tissue P
2 under certain treatment conditions, with the potential cause being either increased local blood flow or decreased local oxygen metabolic consumption due to cellular damage.
Author Keywords: Photodynamic; EPR; Benzoporphyrin derivative; P
2; Oxygen; Photochemotherapy; RIF-1 tumor; Singlet oxygen
Article Outline
*1 This paper was presented as part of ISOTT2000 held in Nijmegen, The Netherlands, August 20–25, 2000. Organizer was Dr Berend Oeseburg.
Corresponding author. Tel.: +1-603-646-3861; fax: +1-603-646-3856; email: pogue@dartmouth.edu
