Abstract
Objective: Anti-programmed cell death ligand 1 (PD-L1) and anti-programmed cell death 1 (PD-1) therapy in cancer treatment cause immune-related adverse events (irAEs), such as hypothyroidism. We investigated the potential of quantitative computed tomography (CT) for early diagnosis and severity assessment of overt hypothyroidism induced by PD-L1/PD-1 treatment.
Methods: Sixty-six patients were enrolled in this study. Patients were divided into two groups: those who developed immune checkpoint inhibitor (ICI) -related hypothyroidism (n=32) and those without thyroid-irAEs (n=34). Using non-contrast CT images, the mean attenuation value of a polygonal region-of-interest delineating the right and left lobes of the thyroid gland was obtained. Longitudinal changes in CT attenuation values of the thyroid gland before and after ICI administration were calculated. Using non-contrast and contrast CT images, the maximum width, length, and anterior-posterior diameter pre- and post-ICI administration were measured to approximate thyroid volume and assess atrophy. Thyrotropin (TSH) levels and levothyroxine doses were analyzed.
Results: The CT attenuation values were significantly decreased in the thyroid-irAE group during or before the TSH levels increase (p＜0.0001). CT attenuation values decreased 43 days before TSH levels increased. High TSH levels and levothyroxine doses were associated with atrophy (r=-0.69, p＜0.0001 and r=-0.52, p=0.01, respectively).
Conclusion: Thyroid CT attenuation values decrease before TSH levels increase in overt hypothyroidism induced by ICIs, which may facilitate early diagnosis of hypothyroidism. Maximum width, length, and anteroposterior diameter measurement can reliably detect thyroid atrophy, which is associated with hypothyroidism severity.
