The patient lies immobile on the operating table. He’s been diagnosed as having bladder cancer and Dr. Ralph Benson Jr., Consultant in the Department of Urology, sits down and goes to work. But rather than preparing to remove the bladder, he inserts a quartz fiber into a cystoscope aimed at the tumor. Wearing special goggles, Dr. Benson peers through the cystoscope and directs a laser beam that will kill the cancer.
Using this experimental procedure in 1982, developed at Mayo, Dr. Benson was able to treat the bladder cancer in minutes. The cancer was destroyed, the bladder was saved, and the patient went home in just a couple of days and was spared the ordeal of a major operation.
The process, called hematoporphyrin derivative phototherapy is an effective treatment for certain kinds of bladder cancers. The process combines the photosensitivity properties of hematoporphyrin derivative (HpD), a naturally occurring derivative of blood, with light delivered from an argon ion pumped dye laser.
Dr. Benson said the process was originally designed to detect cancer in the bladder. “We had patients with a positive urinary cytology,” he said. “The cytologist was telling us there were cancer cells present, but we were unable to find their source during a cystoscopic examination.”
Dr. Benson borrowed a localization technique, developed by Dr. Denis Cortese, Consultant in the Division of Thoracic Diseases, and Dr. James Kinsey, formerly a physicist in the Biodynamics Research Unit, used for detecting tumors in the bronchi, the network of airways in the lungs. They had been using HpD for some time and Dr. Benson thought it could work on bladder cancers. This earlier work had shown that HpD, once injected, is taken up by cancerous cells and then fluoresces under near ultraviolet light.
A “chopping” device delivered rapidly alternating near ultraviolet and white light down the cystoscope. The near ultraviolet light excited fluorescence in cells that had taken up HpD and the white light allowed normal visualization. The fluorescence was detected by a probe and then changed to an auditory signal. “We are now able to localize dysplastic (abnormal) cells in the bladder that otherwise look normal,” said Dr. Benson.
“We wanted to be sure that all abnormal cells took up the HpD” said Dr. Benson. “So, pathology examined bladders that we had to remove anyway for invasive cancer and found that, indeed, the HpD (that had been injected into the patient before surgery) was being taken up into the cancer cells and normal cells were spared.”