Immune-Related Thyroiditis in Patients with Advanced Lung Cancer Treated with Immune Checkpoint Inhibitors: Imaging Features and Clinical Implications

SIMPLE SUMMARY: An immune-related adverse event (irAE) is a unique side effect related to immunotherapy involving many different organs. Immune-related thyroiditis is one of the irAEs, and some patients experience permanent hypothyroidism requiring hormone replacement therapy. There are not many articles investigating the imaging findings of immune-related thyroiditis. We aimed to investigate the incidence and imaging characteristics of restaging chest CT scans, which are routinely performed per oncologic protocol. We found that approximately 10% of patients showed radiologically evident thyroiditis. The gland showed diffuse hypoattenuation or heterogeneous attenuation changes, with enlargement or atrophy of the gland on CT scans. In addition, among patients with thyroiditis, the patients with positive imaging findings were managed more frequently with hormone replacement therapy compared with the patients without positive imaging findings. This article provides an imaging finding of thyroiditis on restaging chest CT scans during immune checkpoint inhibitor therapy that may alert clinicians to the presence of clinically relevant thyroiditis. ABSTRACT: Immune checkpoint inhibitors (ICI) are widely used in advanced nonsmall cell lung cancer (NSCLC) treatment, and the immune-related adverse events involving many organs have been recognized. This article investigated the incidence and imaging characteristics of immune-related thyroiditis in NSCLC patients and correlated the findings with clinical features. A total of 534 NSCLC patients treated with ICI were included. Imaging findings indicative of thyroiditis included changes in morphology and attenuation on restaging chest CT scans and FDG uptake on PET/CT during ICI therapy. Fifty patients (9.4%) had imaging findings indicative of thyroiditis. The median time to onset was 9.5 weeks (range: 0.9–87.4 weeks). The most common finding was diffuse hypoattenuation of the gland (72%), with enlargement in 15 and atrophy in 12 patients. Heterogeneous attenuation of the gland was noted in 12 patients (24%), with enlargement in 7 and atrophy in 1 patient. Two patients (4%) showed increased FDG uptake in the gland on PET/CT without changes in the CT scan. Twenty-two patients who had both clinical and radiologic diagnoses of thyroiditis were more frequently managed with hormone replacement than those with thyroiditis without an imaging abnormality (p < 0.0001). Therefore, awareness of the imaging findings of immune-related thyroiditis may alert clinicians to the presence of clinically relevant thyroiditis.