Long-term results of total lymphoid irradiation in the treatment of cardiac allograft rejection

Abstract

To evaluate the short and long-term effects of total lymphoid irradiation (TLI) in the treatment of cardiac transplant rejection. Between 1986 and 1995, 48 courses of TLI were delivered to 47 cardiac transplant patients. In 37 patients, TLI was administered for intractable allograft rejection despite conventional therapy while 10 patients received TLI prophylactically. The prescribed radiation dose was 8 Gy in 0.8 Gy fractions twice weekly to mantle and inverted-Y plus spleen fields. Postirradiation follow-up ranged from 6 months to 9.1 years, with a mean of 3.1 years. The actual mean dose was 7.3 Gy delivered over a mean of 39 days. Fifty-six percent of patients required treatment delay or abbreviation because of thrombocytopenia, leukopenia, infection, or unrelated problems. In patients treated for intractable rejection, rejection rates dropped from 0.46 to 0.14 and to 0.06 episodes/patient/month before, during, and after TLI (p < 0.0001). Rejection rates continued to drop throughout follow-up. Prednisone requirements decreased from 0.41 mg/kg before treatment to 0.21 mg/kg afterward (p < 0.0001). The ratio of helper to cytotoxic-suppressor T-cells decreased during TLI from 1.33 to 0.89, and remained low at 0.44, 2-4 months after treatment. Infection rates were not increased and two patients developed malignancy. Rejection rates were high during prophylactic treatment and this protocol was abandoned. Three-year actuarial survival after irradiation was 60% for patients with intractable rejection and 70% for the prophylactic cohort. TLI is an effective treatment for control of intractable cardiac rejection. Episodes of rejection and steroid dosage requirements are decreased for up to 9.1 years. A possible mechanism of action is long term alteration in T-lymphocyte subsets. Patients experience transient bone marrow suppression but no increase in infection or bleeding. Long-term complications of TLI are not appreciably different than conventional immunosuppression.