Thyroid abnormalities following the use of cytotoxic T-lymphocyte antigen-4 and programmed death receptor protein-1 inhibitors in the treatment of melanoma.

CONTEXT: Checkpoint inhibitors are emerging as important cancer therapies but are associated with a high rate of immune side effects, including endocrinopathy.

OBJECTIVE: To determine the burden of thyroid dysfunction in patients with melanoma treated with immune checkpoint inhibitors and describe the clinical course.

DESIGN AND PATIENTS: Consecutive patients with melanoma treated with either ipilimumab, nivolumab, pembrolizumab or the combination of ipilimumab and nivolumab were identified. Baseline thyroid function tests were used to exclude those with pre-existing thyroid abnormalities, and thyroid function tests during treatment used to identify those with thyroid dysfunction.

RESULTS: Rates of overt thyroid dysfunction were in keeping with the published phase 3 trials. Hypothyroidism occurred in 13·0% treated with a programmed death receptor-1 (PD-1) inhibitor and 22·2% with a combination of PD-1 inhibitor and ipilimumab. Transient subclinical hyperthyroidism was observed in 13·0% treated with a PD-1 inhibitor, 15·9% following a PD-1 inhibitor, and 22·2% following combination treatment with investigations suggesting a thyroiditic mechanism rather than Graves' disease, and a high frequency of subsequent hypothyroidism. Any thyroid abnormality occurred in 23·0% following ipilimumab, 39·1% following a PD-1 inhibitor and 50% following combination treatment. Abnormal thyroid function was more common in female patients.

CONCLUSION: Thyroid dysfunction occurs commonly in patients with melanoma treated with immune checkpoint inhibitors, with rates, including subclinical dysfunction, occurring in up to 50%.