Photodynamic therapy for solid tumors: A review of the literature

Abstract

Photodynamic therapy (PDT) utilizes a sensitizer agent and light to produce selective cell death. Dermatologists are familiar with PDT for the treatment of actinic keratoses and early nonmelanoma skin cancers, and recent studies have elucidated that PDT has resulted in improved morbidity and secondary outcomes for the treatment of various cancerous and precancerous solid tumors. Light source and dosimetry may be modified to selectively target tissue, and novel techniques such as fractionation, metronomic pulsation, continuous light delivery, and chemophototherapy are under investigation for further optimization of therapy. This article aims to review the expanding indications for PDT and demonstrate the potential of this modality to decrease morbidity and increase quality of life for patients. To illustrate these new indications, we provide a focused review of the latest literature on PDT for dermatologic and other solid tumors including gastrointestinal, peritoneal, lung, genitourinary, brain, breast, and head and neck. Data on efficacy, survival, and side effects vary across tumor types but support PDT for the treatment of numerous solid tumors. With new advances in PDT, indications for this therapeutic modality may expand.

Photochemical Internalization for Intracellular Drug Delivery. From Basic Mechanisms to Clinical Research

“…Of course, ideally, a highly selective sensitizer should obviate any need to protect adjacent tissue, but at the time of writing, such photosensitizers are not yet available for routine clinical practice. Healing usually occurs with almost no scarring and the tissue architecture is also preserved as highlighted previously, which in turn supports the matrix for regeneration of normal undamaged tissue [34].…”

Application of nanotechnology for enhancing photodynamic therapy via ameliorating, neglecting, or exploiting tumor hypoxia

“…These formed radical anions or cations can then react with triplet ground state molecular oxygen ( 3 O 2 ) or water (H 2 O) to generate oxygenated products such as superoxide anion radicals (O 2 •− ), hydroxyl radicals (·OH), and hydrogen peroxides (H 2 O 2 ), which interfere with biological molecules, such as lipids, proteins, and DNA, and eventually kill cancer cells 14 . Alternatively, for type 2 PDT, the 3 PS * transfers its energy directly to the surrounding 3 O 2 to form cytotoxic 1 O 2 15 . Both type I and type II reactions can occur simultaneously, and the ratio of the two depends on several factors, for example, photosensitizer type, molecular oxygen concentration, and substrate category.…”

“…14 Alternatively, for type 2 PDT, the 3 PS * transfers its energy directly to the surrounding 3 O 2 to form cytotoxic 1 O 2 . 15 Both type I and type II reactions can occur simultaneously, and the ratio of the two depends on several factors, for example, photosensitizer type, molecular oxygen concentration, and substrate category. In most cases, the type 2 reaction plays a dominant role in PDT, and thus PDT efficiency is determined by oxygen supply.…”

Optical properties of photodynamic therapy drugs in different environments: the paradigmatic case of temoporfin

“…Today the therapeutic use of light has evolved considerably, particularly owing to the milestone discovery and application of photodynamic therapy (PDT). 9,10 In this context, a drug that is inert in the dark is administered to a patient, either topically or systemically, and the region in which the lesion is localized is then irradiated, usually with visible or infrared light. 11 The absorption of light by the drug -the photosensitizer -triggers photophysical pathways leading to the disruption of biological macromolecules (nucleic acids, proteins, or lipid membranes) and, consequently, to cell death, and ultimately to the eradication of the lesion.…”