TreatmentUpdate41: Vol. 4, No. 1 - March, 1993
Sean Hosein

In diseases other than HIV infection radiation is used to treat ITP (idiopathic thrombocytopenic purpura; abnormally low levels of platelets). Last year, doctors in the USA reported on their success in treating ITP in people with HIV infection. In the past, these subjects received AZT, antibody infusions and immunosuppressive steroids (prednisone). None of those therapies increased the platelet count without reducing the patients' quality of life. The doctors then tried radiation therapy. Radiation directed at the spleen in doses of "100 cGy twice per week" was given for 4 to 5 weeks. In 2 of the subjects the number of platelets increased by the second week of treatment. In the third subject the platelet level started to increase before radiation therapy started. The doctors think that steroids given to the third patient caused the increased platelet count.

Why Radiation Worked

Radiation treatment probably suppresses some of the immunofunctions in the spleen. This reduction in immunofunctions likely reduces the efficency of the spleen in destroying platelets. The doctors gave low doses of radiation because they thought that higher doses would have caused a severe suppression of the immune system. Although radiation can be used to damage HIV, the doses used on these subjects were not high enough to have significant anti-HIV effects.

References:

1. Needleman SW, Sorace J, and Pousinn-Rosillo H. Low-dose splenic irradiation in the treatment of autoimmune thrombocytopenia in HIV-infected patients. Annals of Internal Medicine 1992;116:310-311.

2. Conway B and Tomford WW. Radiosensitivity of human immunodeficiency virus type 1. Clinical Infectious Diseases 1992;14:978-979

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