Tumor destruction in photodynamic therapy is the result of the combination of direct cellular toxicity and damage to tumor microvasculature. These phenomena appear to be caused by tissue interactions with toxic oxygen compounds which are formed when light interacts with photosensitizing agents. Although injury to cell membranes, mitochondria and the nucleus have been noted, such injuries by themselves tend to be sublethal and cannot totally account for the effectiveness of PDT. The mechanism of effect of PDT on the vasculature has not been fully investigated. The vascular effects are believed to involve both intravascular and perivascular phenomena. Platelet aggregation appears to be an early event. Changes to the endothelium, and smooth muscle contraction as well as increased capillary permeability have also been observed during therapy. Initial experiments using'cyclooxygenase inhibitors indicate that arachidonic acid metabolites are active elements in producing the vascular phase of the therapeutic response and that these microvasculature effects appear to be critical to permanent tumor destruction.

Date Published: 13 June 1989
PDF: 17 pages
Proc. SPIE 1065, Photodynamic Therapy: Mechanisms, (13 June 1989); doi: 10.1117/12.952016

Published in SPIE Proceedings Vol. 1065:
Photodynamic Therapy: Mechanisms
Thomas J. Dougherty, Editor(s)