Study of Photodynamic Therapy in Patients With Prostate Cancer Following Radiation Therapy

Prostate cancer is a leading cause of morbidity and mortality in men around the world. Because of the worldwide increase in life expectancy, a dramatic increase in the number of patients with prostate cancer is expected. It has been estimated that by the year 2002, 92,000 men over 65 years of age were diagnosed annually in the European community, where prostate cancer will account for 12% of all new male cancer diagnoses. Consequently, radiation therapy is used extensively for primary therapy of prostatic carcinoma. The Management Report of clinically localized prostate cancer by the National Cancer Institute SEER program indicated that 30% of patients choose radiation therapy as their first treatment option. However, the ability of radiation therapy to totally and permanently eradicate prostatic cancer has come under question recently as a result of the high number of patients who have post radiotherapy elevated prostatic specific antigen (PSA) determinations (85%), and the high positive post irradiation biopsy rate (31 90%). With high local recurrence rates possibly influencing death rates, the recurrence of prostate cancer after potentially curative local therapy is becoming a significant urological problem. As patients are being treated for prostate cancer at a younger age, a significant number of them will ultimately fail the primary treatment and will be candidates for safe and potentially curative salvage therapy. High complication and morbidity rates associated with current salvage therapies demand new and improved means for eradicating recurrent local disease. Photodynamic therapy, which allows the destruction of a tumor by the IV administration of a photosensitizer and the local application of light, may provide such means. Transperineal interstitial photodynamic therapy is a minimally invasive procedure to treat selected patients with failed radiation therapy of prostate cancer. A preliminary phase 1 study using the photosensitizer meso-tetrahydroxyphenyl chlorine (mTHPC) in 14 patients indicated that PDT could produce necrosis in prostate involving cancers recurring after radiotherapy, with a low incidence of complications.