Thyroid function abnormalities associated with the chronic outpatient administration of recombinant interleukin-2 and recombinant interferon-alpha

Abstract

We prospectively examined thyroid function during and following chronic, outpatient therapy with recombinant interleukin-2 (rIL-2) and Roferon-A (rIFN-alpha 2a). Twenty-two of 30 patients with advanced renal cell carcinoma treated on a phase II open pilot study of concomitant rIL-2 and rIFN-alpha 2a were included. Serum levels of thyroxine, triiodothyronine, free thyroxine index, thyrotropin, antithyroid antibodies, and thyrotropin (TSH) receptor binding antibodies were measured before therapy and after every other cycle. Selected patients underwent studies after every cycle and following completion of therapy. Twenty patients (91%) developed laboratory evidence of thyroid dysfunction, 11 (50%) developed hypothyroidism, five (23%) had a biphasic pattern, and four (18%) had hyperthyroidism. The incidence of thyroid dysfunction increased with increased number of treatment cycles. Transient hyperthyroidism was noted in six of the 11 patients studied after the first cycle and persisted after cycle three in only two patients. Hypothyroidism was not observed after cycle 1, but became increasingly frequent between cycles 2 (56%) and 6 (90%). Thyroid function normalized following therapy in nine of 12 patients tested. Antithyroid antibodies were identified pretherapy in five patients (23%) and de novo in none; TSH receptor binding antibodies were not detected. This study demonstrates a remarkably high frequency of reversible thyroid dysfunction in patients with advanced renal cell carcinoma treated with repeated cycles of rIL-2 plus rIFN-alpha 2a. We conclude that chronic therapy with rIL-2 and rIFN-alpha 2a produces thyroid dysfunction in virtually all patients most likely secondary to a nonspecific, nonautoimmune, toxic manifestation of prolonged treatment. IL-2 therapy may, therefore, produce thyroid dysfunction by more than one mechanism.