Absence of bone marrow toxicity in elderly patients treated with recombinant human thyroid-stimulating hormone and empirically dosed radioiodine for thyroid cancer

OBJECTIVES: The purpose of this paper is to evaluate the rate of clinically significant bone marrow toxicity in elderly patients after recombinant human thyroid-stimulating hormone (rhTSH) and empirically dosed radioiodine therapy for thyroid cancer. METHODS: This is a retrospective review of 15 patients with differentiated thyroid cancer that were at least 70 years old at the time of their first radioiodine treatment at our institution administered by the authors under a protocol involving an empiric dose prescription and preparation with rhTSH rather than hypothyroidism. The median dose per administration was 203 mCi and the median total dose per patient was 234 mCi. One third of the patients had at least 1 positive posttreatment whole-body scan and the other two thirds all had negative posttreatment whole-body scans. The primary study endpoint was a red cell, white cell, or platelet count below the lower limit of the normal range that produced symptoms or resulted in a recommendation for treatment. Complete blood count follow-up was at least 1 year in all patients, with a median value of 4 years. RESULTS: There was no evidence of clinically important bone marrow toxicity from radioiodine therapy in the patients in this study. No patient required treatment for anemia, leucopenia, or thrombocytopenia. CONCLUSIONS: In patients with normal renal function, clinically significant bone marrow toxicity from radioiodine therapy is highly unlikely with rhTSH preparation and empiric dosing with <250 mCi per administration and total cumulative doses <350 mCi.