Expert opinion on thyroid complications in immunotherapy.

Thyroid pathologies are the most common forms of endocrinopathy under anticancer immunotherapy. Frequency ranges from 3% to 22% for hypothyroidism and 1% to 11% for thyrotoxicosis. Risk is higher with anti-PD-1 than anti-CTLA-4 treatment and higher again with associated treatment. Pathophysiology mainly consists in silent inflammatory thyroiditis, which accounts for the usual presentation of transient thyrotoxicosis followed by hypothyroidism. Therapeutic strategy usually consists in monitoring with or without symptomatic treatment in case of thyrotoxicosis, and levothyroxine replacement therapy in case of symptomatic hypothyroidism or TSH>10 mIU/L. Screening for dysthyroidism should be systematic ahead of treatment and before each immunotherapy injection for the first 6 months, then at a lower rhythm. It comprises clinical assessment and TSH assay. Onset of thyroid dysfunction should not interrupt immunotherapy, being mainly transient, easy to treat and mild. Teamwork between oncologists and endocrinologists improves screening and management, so as better to accompany the patient during treatment.