Reduction in thyroid volume in chronic myeloid leukemia patients after imatinib treatment: a longitudinal study

Introduction: Thyroid atrophy is frequently observed following sunitinib treatment. This has been attributed to sunitinib-induced degeneration of the thyroid follicular cells. However, the effect of imatinib mesylate (IM), which has a similar pharmacological profile to that of sunitinib on thyroid volume, has not previously been studied. Importantly, IM remains the mainstay of treatment for Nigerian chronic myeloid leukemia (CML) patients. The aim of this study was to evaluate the effect of continuous IM use on thyroid volume in BCR::ABL1 positive CML patients. Material and methods: This longitudinal case-controlled study included 50 IM-naïve patients with BCR::ABL1 positive CML and 50 controls with no underlying thyroid disorders. Thyroid ultrasonography was done for all subjects at recruitment, and again after six months of treatment for the CML patients on IM using a LOGIQ TM P9 ultrasound machine. Total thyroid volume (TTV) was determined from the measured thyroid parameters. Results: The median age (range) in years of the two groups (CML patients vs controls) was 40.0 (18–65) vs 38.5 (18–63) (p = 0.251). Twenty-three (46%) of the CML patients and 21 (42%) of the controls were males. The median (range) TTV of the CML patients at baseline vs 6 months was 7.6 (3.3–27.7) mL vs 7.8 (3.4–22.8) mL (p = 0.660). Sub-analysis showed a significant reduction in the median TTV at 6 months in the male CML patients i.e. baseline vs 6 months [8.4 (3.26–19.81) vs 7.3 (2.40–14.53)] (p = 0.021). Conclusions: This study shows that prolonged imatinib use is associated with a significant reduction in total thyroid volume only in male CML patients. Therefore, serial volumetric analysis of the thyroid gland and thyroid function tests in CML patients on IM may be highly desirable.