Cancer phototherapy: illuminating blood.

Cancer phototherapy: Illuminating blood

Blood cell cancers can be particularly tricky to treat. Unlike solid tumors, they are not candidates for surgery--you can't permanently remove someone's blood. New, a New York researcher has devised a novel approach called extracorporeal photopheresis, which involves treating blood outside the body with a drug activated by light.

The developers hope the procedure will also be useful in autoimmune diseases, in which the immune system attacks the body. Initial evaluation for safety and efficacy has just begun at six U. S. and European institutions. Columbia University's Richard Edelson, who designed the technique, described it at last week's American Cancer Society seminar in San Diego.

In the past three years, Edelson and his colleagues have treated 11 patients suffering from cutaneous T cell lymphoma. In this type of cancer, which Edelson says has a median survival rate of about three to five years, the body produces too many T cells, white blood cells that are part of the immune system.

The patients were given psoralen, a drug activated by ultraviolet light and currently used to treat psoriasis (SN: 5/22/82, p. 346). Since ultraviolet light is absorbed by the skin, the problem is getting it to the blood-borne psoralen where it is needed. Edelson and his colleagues remove some blood from the patient, separate out a solution of mostly white blood cells and return the rest to the body. Before they reinfuse the white blood cell fraction, they expose it to ultraviolet light, which activates the psoralen for a few thousandths of a second. The activated psoralen disrupts the white blood cells by causing extensive crosslinking of the DNA.

Eight of the 11 patients treated thus far have shown a decrease in T cells; two of them have been taken off therapy and have not suffered a recurrence. The disease treatment, notes Edelson, is not a cure--it eliminates some of the extra cells, but it doesn't halt their production. Many other diseases involve T cells, and, he says, "what we are really after is the treatment of immune diseases.'

Bruce Wintroub, who is conducting a trial of extracorporeal photopheresis at the Veterans Administration Medical Center in San Francisco, says finding photoactive drugs that will work against specific types of blood cells involved in different types of diseases is key to extending the therapy's uses. "The more specific you can make the chemical you're going to activate,' he says, "the more specific you can make the treatment.'

Edelson is awaiting Food and Drug Administration approval to use the ultraviolet light device on patients with autoimmune diseases.