Computed tomography imaging findings of nivolumab-induced thyroid dysfunction

The thyroid gland is most frequently involved in immune-related adverse events (irAEs) by nivolumab. We reviewed the thyroid function and thyroid gland volume and volume change ratio between baseline and follow-up CT (volume follow-up/volume baseline) in 24 patients treated with nivolumab for lung cancer and renal cell carcinoma. Among them, four (16.7%) demonstrated nivolumab-induced thyroid dysfunction that shows either hypothyroidism or hyperthyroidism. Three and one cases were treated with nivolumab for lung cancer and renal cell carcinoma, respectively. Two patients with hypothyroidism (cases 1 and 2) showed reduced thyroid volume (volume change ratio: 0.80 and 0.84) on computed tomography (CT) images. Besides, remarkably diminished CT attenuation of the thyroid gland was observed in a patient with hypothyroidism (case 2). One of the two patients with hyperthyroidism showed increased thyroid volume (volume change ratio: 1.32) (case 3), whereas no difference in the thyroid gland volume was observed between the previous and follow-up CT in another patient with hyperthyroidism (case 4). Thyroid volume change ratio >0.1 was observed even in 6 of 20 (30%) patients without thyroid dysfunction. Considering the wide use of nivolumab in cancer treatment, radiologists should be aware that changes in the thyroid volume and attenuation on CT are associated with thyroid dysfunction caused by nivolumab, as well as thyroid volume may change even in patients with normal thyroid function during nivolumab therapy.