Photodynamic therapy: a promising new modality for the treatment of cancer

Abstract

The first reports on photodynamic therapy (PDT) date back to the 1970s. Since then, several thousands of patients, both with early stage and advanced stage solid tumours, have been treated with PDT and many claims have been made regarding its efficacy. Nevertheless, the therapy has not yet found general acceptance by oncologists. Therefore it seems legitimate to ask whether PDT can still be described as "'a promising new therapy in the treatment of cancer".Clinically, PDT has been mainly used for bladder cancer, lung cancer and in malignant diseases of the skin and upper aerodigestive tract. The sensitizer used in the photodynamic treatment of most patients is Photofrin®, (Photofrin®, the commercial name of dihematoporphyrin ether/ester, containing > 80% of the active porphyrin dimers/oligomers (A.M.R. Fisher, A.L. Murphee and C.J. Gomer, Clinical and preclinical photodynamictherapy, Review Series Article, Lasers Surg. Med., 17 (1995) 2-31 ). It is a complex mixture of porphyrins derived from hematoporphyrin. Although this sensitizer is effective, it is not the most suitable photosensitizer for PDT. Prolonged skin photosensitivity and the relatively low absorbance at 630 rim, a wavelength where tissue penetration of light is not optimal, have been frequently cited as negative aspects hindering general acceptance. A multitude of new sensitizers is currently under evaluation. Most of these "second generation photosensitizers" are chemically pure, absorb light at around 650 nm or greater and induce no or less general skin photosensitivity. Another novel approach is the photosensitization of neoplasms by the induction of endogenous photosensitizers through the application of 5-aminolevulinic acid (ALA). This article addresses the use of PDT in the disciplines mentioned above and attempts to indicate developments of PDT which could be necessary for this therapy to gain a wider acceptance in the various fields.

Spectrroscopic Sensing of Cancer and Cancer Therapy: Current Status of Translational Research

“…PDT is being investigated for treatment of a variety of cancers. For recent reviews see Schuitmaker et al 66 Dougherty et al 67 and Chang and Bown. 68 PDT is also being investigated for use in non-malignant diseases such as rheumatoid arthritis 69 and the selective ablation of endometrial tissue.…”

Photodynamic parameters in the chick chorioallantoic membrane (CAM) bioassay for topically applied photosensitizers

“…Photodynamic therapy (PDT), also called photochemotherapy, is a new modality for the treatment of cancer [1][2][3] and a variety of nononcologic conditions [3][4][5][6][7]. PDT is based on administering a photosensitizer, which is preferentially retained in tumor (and other proliferating) tissue.…”

Photodynamic therapy: A mitochondrial inducer of apoptosis

“…PDT is an FDA-approved form of cancer therapy involving the somewhat selective photosensitization of neoplastic cells, usually with porphyrins or porphyrin-like drugs. The delivery of a suitable light dose to photosensitized tissues can result in a highly-localized eradication of neoplastic lesions 9 with minimal damage to adjacent host tissues. Several groups have now reported that PDT can initiate a rapid apoptotic response.…”