UV Zapping Of T-Cells
Photopheresis is a medical treatment process used to treat a variety of diseases, one of which is GVHD. It is touted as the least toxic treatment strategy available for GVHD.
Generally speaking, Extracorporeal Photopheresis (ECP) exposes a patient's blood to 8-methoxypsoralen followed by UVA irradiation before returning the blood to the patient.
The photo to the left is of a Photopheresis machine. This is just one version; there are several other models.
In a Photopheresis treatment, an IV is started if a central line or PICC is absent. The IV is attached to the Photopheresis treatment machine. Blood is withdrawn from the patient (pumped out of the patient thorugh the IV) and fed into a bag until a sufficient quantity is gathered (about two cups). The blood is then spun down to extract the white blood cells, and the red cells and white cells are separated. Red cells are deposited into a separate bag and fed back into the patient. White cells are deposited into a series of tubing that rests under a UV light. The white cells are treated with the UV rays, and fed back into the patient through the same IV used to extract them. It is simular to a dialysis, except that the blood is not filtered.
length of treatment
Typically, Photopheresis treatments last for 6-12 weeks.
Almost immediately (within 24-48 hours), a systematic destruction of leukocyte blood cells (called apoptosis) occurs. That process causes the bad T-cells cells to be suppressed and regularory T-cells to be introduced.
According to the Cancer Center of Seattle, Washington, 86% of patients with Grade II Acute GVHD recovered, 55% with Grade III and 30% with Grade IV. Complete recovery was seen in 82% of those with skin GVHD, 61% of those with liver and gut GVHD.
At the 4-year mark, 22 of 28 patients had no signs of GVHD. Transplant-related mortality at 4 years for patients with complete remission were 14%; for those without complete remission, it was 73%.
Photopheresis treatments can also result in reduction or discontinuance of steroids, without Acute GVHD flaring.
Other uses of phototherapy & Photopheresis
Phototherapy is used to treat other T-cell diseases, such as cutaneous T-cell Lymphoma, dermatological disorders and organ transplant rejection.
We'll defer the more technical aspects of Photopheresis to the more knowledgeable folks, such as Dr. M. Owsianowski, or Dr. Hildegard T. Greinix, and Dr. Fred Hutchinson Cancer Research Center, Seattle, WA as published in the Blood Journal as an excellent source of sound information.