Photodynamic Therapy for Cancer

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Surgery, chemotherapy, and radiation are not enough to cure all cancers. Photodynamic therapy is a newer approach with potential to improve treatment outcomes.

“Although still emerging, it is already a successful and clinically approved therapeutic modality used for the management of neoplastic and nonmalignant diseases,” reported Dr. Patrizia Agostinis Catholic University of Leuven in Belgium and colleagues from 22 research institutions in Europe and the United States. These authors provided a detailed review of photodynamic therapy for cancer.

With fiber optic technology, photodynamic therapy can be delivered to tumors almost anywhere in the body. The light does not kill cells by itself.

Photosensitizer drugs are administered before the photodynamic procedure. The light causes the photosensitizers to react with oxygen to form a highly energetic state called singlet oxygen, which then attacks the tumor cells.

For cancers that are readily accessible, such as skin cancers, the photosensitizer drug can be applied to the surface. For internal tumors, photosensitizer drugs are chosen to accumulate preferentially in the cancer cells. Research is ongoing to find the optimum way to target photosensitizers to specific cancer types.

The advantages of photodynamic therapy (PDT) are lower toxicity and fewer side effects, compared to other cancer treatments. “Paradoxically, the highly localized nature of PDT is one of its current limitations,” Agostinis added.

It is not practical for metastatic cancer. However, it can be used in combination with surgery, chemotherapy, and radiotherapy.

“PDT is still considered to be a new and promising anti-tumor strategy. Its full potential has yet to be shown,” Agostinis wrote.

According to the American Cancer Society's web site, photodynamic therapy is already in clinical use to treat the following types of cancer:

1. Esophageal

2. Endobronchial, a type of non-small cell lung cancer affecting the lining of the bronchial tubes

3. Skin cancers of the basal cell carcinoma and squamous cell carcinoma types

4. Gynecological cancers of the vagina, vulva, and cervix

The government web site http://clinicaltrials.gov/ reports trials in progress (Sept. 20, 2011) for photodynamic therapy to treat cancers of the brain, gall bladder, urinary bladder, prostate, liver, breast, peritoneal cavity, and head and neck.

References:

1. Agostinis P et al, “Photodynamic therapy of cancer: an update”, CA: A Cancer Journal for Clinicians 2011; 61: 250-281. http://www.ncbi.nlm.nih.gov/pubmed/21617154

2. American Cancer Society. Photodynamic Therapy. Web. Sept. 20, 2011.
http://www.cancer.org/Treatment/TreatmentsandSideEffects/TreatmentTypes/photodynamic-therapy

Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.

Reviewed October 26, 2011
by Michele Blacksberg RN
Edited by Jody Smith

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