Endocrine Abstracts

Introduction: Tyrosine Kinase Inhibitors (TKIs) are approved for the treatment of several cancers and can induce hypothyroidism by unclarified mechanisms.

Objectives: To assess the prevalence of hypothyroidism in patients treated with TKIs.

Methods: Retrospective review of clinical records of patients treated with TKIs in our institution between 2003 and 2009. We evaluated parameters such as sex, oncologic pathology, TKI used, TSH and free T₄, dose of levothyroxine.

Results: We evaluated 37 patients, 20 were men (54%) and 17 women (46%). Imatinib was used in 24 patients, sunitinib in 11, lopatinib in 1 and sorafenib in another. Twenty-one patients (56.8%) had gastrointestinal stromal tumour, 8 (21.6%) chronic myeloid leukaemia, 6 (16.2%) renal cell carcinoma, 1 (2.7%) breast cancer and 1 (2.7%) hepatocellular carcinoma. Thyroid function tests (TFT) were assessed prior to treatment with TKI in 6 patients (all euthyroid) and during or after treatment with TKI in 13 patients (35.1%). Of these 13 patients, 6 were hypothyroid (46.2%) after a mean period of 12.2±5.2 months of TKI therapy. Thyroid function was not evaluated in 24 of 37 patients (64.9%). Only 3 out of 24 patients treated with imatinib were screened for thyroid dysfunction and all were euthyroid. TFT were assessed in 8 of the 11 patients treated with sunitinib, 5 of which were hypothyroid (62.5%). The patient treated with sorafenib was euthyroid and the one treated with lopatinib had hypothyroidism.

Conclusion: A high percentage of patients was not screened for thyroid dysfunction. The prevalence of hypothyroidism in the patients who performed TFT was 46.2%. Sunitinib seems to induce hypothyroidism more frequently. It is important to consider this TKI adverse effect and include TFT in routine toxicity assessment of these patients.