THYROID-DYSFUNCTION FOLLOWING BONE-MARROW TRANSPLANTATION USING HYPERFRACTIONATED RADIATION

Thyroid dysfunction has been reported following single dose and fracti onated radiation in the context of bone marrow transplantation (BMT). Limited data are available regarding this complication following hyper fractionated radiation. We undertook a retrospective analysis of thyro id function in 150 patients who received BMT at our institution, and w ho were alive and disease-free for at least 1 year after transplant. T here were 100 pediatric patients and 50 adult patients, with a median follow-up of 6.2 years far the whole group. These patients had acute ( n = 91) or chronic leukemias (n = 36), severe aplastic anemia (n = 18) or immunodeficiency disorders (n = 5). The majority of the patients r eceived radiation-based cytoreductive regimens including 129 patients who received hyperfractionated total body irradiation (TBI) to a total dose of 1375 cGy or 1500 cGy and 10 patients who received total lymph oid irradiation (TLI) to a total dose of 600 cGy, Twenty two patients of the cohort of 150 patients (14.7%) and 21 of the 139 patients (15.1 %) who received hyperfractionated radiation were found to have develop ed hypothyroidism, 11-88 months after transplant (median 49 months), E ight patients had received 1375 cGy and 12 patients 1500 cGy TBI, whil e one patient was treated with 600 cGy TLI and one patient was treated with chemotherapy only (busulfan and cyclophosphamide). Three patient s had primary thyroid failure with an elevated TSH and a low T4 index, while 19 patients had compensated hypothyroidism with an elevated TSH but a normal T4 index. Six of eight patients with untreated compensat ed hypothyroidism recovered spontaneously. Statistical analysis reveal ed no significant difference in the incidence of thyroid dysfunction a t 6 years after transplant for any of the following risk factors: age, sex, diagnosis, dose of TBI, type of BMT or the presence or absence o f chronic GVHD. In summary, we observed primary hypothyroidism. in 15. 1% of patients following BMT using hyperfractionated radiation, which is lower than that described after a single dose, but comparable to th at associated with fractionated irradiation.