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STUDY: Photodynamic Therapy
JOURNAL: Journal of Urology 2002;168:1427-1432.
AUTHORS: Timothy R. Nathan
ABSTRACT: Researchers may have added prostate cancer to the list of cancers that can benefit from photodynamic therapy (PDT), which combines drugs and light to treat cancer and other conditions.
COMMENTARY: Timothy R. Nathan of the University College London Hospital in the UK and his colleagues report that most patients treated with PDT, whose prostate cancer had returned following radiation treatment, appear to benefit from the new therapy.
Specifically, the authors report, more than half of treated patients experienced a decrease in their blood levels of PSA, a protein produced by the prostate gland that is often elevated in the presence of prostate cancer. In addition, more than one third of PDT-treated men showed no trace of cancer from a post-treatment biopsy.
Photodynamic therapy is a new option that could be suitable for organ confined prostate cancer recurrence after radiotherapy. These results suggest that photodynamic therapy merits further investigation.
PDT is a two-step therapy that is already being used to treat head and neck cancers, especially esophageal cancers. The first step is to give the patient a light-activated drug such as Photofrin, which tends to collect in tumors. The drug makes the abnormal tissue particularly sensitive to light. The second step is to shine a laser light on the drug-saturated tumors for a brief period of time. There are several PDT drugs available, and each is activated by different wavelengths of light.
Recent reports have suggested that PDT may also help treat cancers of the pancreas, lung and breast.
During the current study, Nathan and his team administered PDT to 14 men. All patients had prostate cancer that had returned following treatment with radiation, as indicated by an increase in PSA and results from a biopsy.
After the procedure, the researchers noted that PSA levels decreased in 9 patients, reaching undetectable levels in 2 patients. Biopsies of 5 patients showed that they were tumor-free. Scans showed that PDT had destroyed up to 91% of the prostate tissue.
A few of the patients experienced side effects after the treatment, Nathan and his team note. Four of the men reported stress incontinence, meaning they leaked urine as a result of laughing, coughing, sneezing or exercise, which began to gradually improve over time. Seven of the participants were able to have intercourse before PDT, and 4 reported a decrease in their abilities after receiving light therapy. This side effect did not appear to diminish over time, the authors report in the October issue of the Journal of Urology.
Complications were no worse among the patients than among studies of patients given surgery or cryotherapy to treat prostate tumors that had returned after treatment. And, the researchers note, complications could be reduced by dosage adjustment.