Long used in the fight against cancer, radiation therapy has been found to have a new application.
Investigators at Stanford University have reported the successful use of total lymphoid irradiation (TLI) to prevent organ rejection in heart transplant patients. The findings were reported in November by Richard Hoppe, MD, and colleagues in the International Journal of Radiation Oncology Biology Physics (1997;39:953-960).
Radiation in low doses proved to be an alternate way of suppressing the immune system’s rejection of transplanted hearts when conventional therapies had failed. The study used a radiation oncology program patterned after therapy used for Hodgkin’s disease, but required only 20% of the amount of radiation used for treating Hodgkin’s.
In the study, 37 patients received TLI for intractable allograft rejection that occurred despite conventional treatment. The patients had "a significantly reduced T-lymphocyte helper to suppressor ratio during and after radiotherapy, which may be a mechanism of increased allograft tolerance," Dr. Hoppe and colleagues reported. They also noted that the radiation therapy was more effective when it was used later rather than immediately after transplantation.
However, another ten patients received TLI as prophylaxis for transplant rejection and experienced increased rates of rejection during prophylaxis.
The authors concluded that the study could lead to "a role for induction TLI in selected high-risk patients or those who cannot tolerate immunosuppressive medications."
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Dr. Hoppe is chairman of the Department of Radiology at Stanford and chairman of the board of the American Society for Therapeutic Radiology and Oncology.
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