Thyroid Functional Status in Patients with Chronic Myeloid Leukemia on TKIS - Single - Center Results

Background: Tyrosine kinas inhibitors (TKI) as target specific compounds profoundly changed the outcome in patients with chronic myeloid leukemia (CML). TKI-induced thyroid dysfunction is now recognized as a common toxicity associated with some TKI. In the previous decade, cases of thyroid dysfunction have been reported in patients treated with different TKIs. Aims: To evaluate the thyroid functional status in CML patients treated with
imatinib and nilotinib. Methods: This cross-sectional study comprised 85 patients with CML in chronic phase, treated with imatinib and nilotinib, at the Clinic for Hematology, Clinical Centre of Vojvodina, Serbia. Thyroid function was assessed by analyzing the serum FT3, FT4 and TSH levels. Hypothyroidism in relation with TKI therapy was defined as newly diagnosed hypothyroidism (while the patient was already on TKI therapy) requiring hormone substitution therapy or serum fT4 level <11,5 pmol/l and TSH >5.50 mIU/l. Patients with previous medical history of thyroid dysfunction were excluded. The duration of TKI treatment varied from 2 month to 10 years. The dose of imatinib was 400mg daily, while nilotinib was dosed 800mg a day. Results: From the total number of patients included, 37 (43,53%) were female and 48 (56,47%) were male. Mean age was 56,71 age (range 21-84). The prevalence of hypothyroidism (clinical, and subclinical) was 8,23% (n=7) which is in
accordance with the prevalence in genera population. Three patients (3,53%) were diagnosed to have subclinical hypothyroidism (defined as normal serum fT4 and TSH >5.50 mIU/l). Hypothyroidism was more common in males (71,5%, p= 0,29, not statically significant). In patients treated with imatinib, 2 (3,4%) had subclinical, while 3 (5,01%) had clinical hypothyroidism. Of the 26 patients treated with nilotinib, subclinical hypothyroidism was detected in 1 (3,85%), as well as clinical hypothyroidism (3,85%). Other thyroid dysfunctions were not detected.
Summary/Conclusions: Hypothyroidism was the only thyroid dysfunction in our cross-sectional study. The prevalence of hypothyroidism in our study group did not differ from general population. Additional study on a larger sample size and evaluation of antibodies is required.