For patients who get hematopoietic stem cell transplants to replace damaged blood-forming stem cells in the bone marrow, the benefits are multiple. In addition to healthy white cells, platelet counts, and hematocrit counts, the patient receives a new immune system that can ward off recurrence of the cancer.
The most common complication of hematopoietic stem cell transplants involving a donor is graft-versus-host disease (GVHD), which can be acute and occur early after transplant (usually in the first three months) or chronic. In acute GVHD, the transplanted stem cells–turned WBCs attack certain areas of the body, most often the skin, liver, and digestive tract. Typical treatment for GVHD involves suppressing the patient’s immune system. But for hematopoietic stem cell recipients, says Daniel Couriel, MD, MS, this means counteracting the effects of the transplant.
"We’re offering the patient a new immune system that will actually kill cancer. When you immunosuppress the patient, you’re blunting the immune system. You’re preventing it from keeping the cancer at bay," he says.
Dr. Couriel is director of the Huntsman Cancer Institute (HCI) Blood and Marrow Transplant Program and professor of internal medicine at the University of Utah School of Medicine. Dr. Couriel performs a treatment called photopheresis to treat graft-versus-host disease. The treatment involves removing whole blood from the patient and centrifuging it. The plasma and erythrocytes are returned to the patient, while the buffy coat—the white cell component—is mixed with a photosensitizing agent and exposed to ultraviolet light.
"The cells treated with light go through apoptosis," explains Dr. Couriel. "When the patient receives the buffy coat, macrophages eat up the cells and generate signals that tell the immune system to tone down."
Dr. Couriel says the treatment seems to modulate the immune system, not suppress it. "This is very important because we don’t want to make the patient susceptible to infections or to recurrence of cancer," says Couriel.
Despite the fact that about 70% of all photopheresis treatments done in the United States are for graft-versus-host disease, the treatment is actually only FDA-approved to treat cutaneous T-cell lymphoma. Researchers aren’t clear why a treatment that calms down the immune system would also work to kill cancer cells. Dr. Couriel says one theory is that processing the lymphoma cells using this technology results in a "vaccination" effect against the disease.
"What seems to be important is what your baseline is," Dr. Couriel says. "If your immune system is activated, photopheresis is going to have one effect. If your immune system is down, photopheresis is going to have a different effect."
In addition to treating graft-versus-host disease and cutaneous T-cell lymphoma patients, photopheresis can be used to treat solid organ transplant rejection, including cardiac and lung transplant. HCI also holds a half-day photopheresis clinic once a month with doctors from dermatology and rheumatology to treat nonmalignant autoimmune diseases. Dr. Couriel encourages physicians to contact HCI if they think photopheresis may benefit their patients.
"There’s a lot of work to be done and we want to find out how it works here," says Couriel. "We want to attach a translational component to all of our studies so we can better learn how to harness the benefit of this technology."