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Effect of Photosensitizer Dose on Fluence Rate Responses to Photodynamic Therapy †
Author(s) -
Wang HsingWen,
Rickter Elizabeth,
Yuan Min,
Wileyto E. Paul,
Glatstein Eli,
Yodh Arjun,
Busch* Theresa M.
Publication year - 2007
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2007.00139.x
Subject(s) - photosensitizer , photodynamic therapy , fluence , oxygen , chemistry , oxygenation , medicine , nuclear medicine , cancer research , photochemistry , ion , organic chemistry
Photodynamic therapy (PDT) regimens that conserve tumor oxygenation are typically more efficacious, but require longer treatment times. This makes them clinically unfavorable. In this report, the inverse pairing of fluence rate and photosensitizer dose is investigated as a means of controlling oxygen depletion and benefiting therapeutic response to PDT under conditions of constant treatment time. Studies were performed for Photofrin‐PDT of radiation‐induced fibrosarcoma tumors over fluence rate and drug dose ranges of 25–225 mW cm −2 and 2.5–10 mg kg −1 , respectively, for 30 min of treatment. Tumor response was similar among all inverse regimens tested, and, in general, tumor hemoglobin oxygen saturation (SO 2 ) was well conserved during PDT, although the highest fluence rate regimen (225 mW × 2.5 mg) did lead to a modest but significant reduction in SO 2 . Regardless, significant direct tumor cell kill (>1 log) was detected during 225 mW × 2.5 mg PDT, and minimal normal tissue toxicity was found. PDT effect on tumor oxygenation was highly associated with tumor response at 225 mW × 2.5 mg, as well as in all other regimens tested. These data suggest that high fluence rate PDT can be carried out under oxygen‐conserving, efficacious conditions at low photosensitizer dose. Clinical confirmation and application of these results will be possible through use of minimally invasive oxygen and photosensitizer monitoring technologies, which are currently under development.