Risk of Thyroid Dysfunction in PD-1 Blockade Is Stratified by the Pattern of TgAb and TPOAb Positivity at Baseline

Positive antithyroglobulin (TgAb) and/or antithyroid peroxidase antibodies (TPOAb) at baseline indicate a high risk of thyroid immune-related adverse events (irAEs) induced by antiprogrammed cell death-1 antibodies (anti-PD-1-Ab). However, whether the positivity patterns of both antibodies are associated with the risk of thyroid irAEs is unknown.

The aim of the present study was to clarify the association of the pattern of TgAb and TPOAb positivity at baseline with the risk of thyroid irAEs induced by anti-PD-1-Ab.

Patients (n = 516) were evaluated for TgAb and TPOAb at baseline and prospectively for thyroid function every 6 weeks for 24 weeks after initiating anti-PD-1-Ab.

Fifty-one (9.9%) patients developed thyroid irAEs (thyrotoxicosis in 34, hypothyroidism without prior thyrotoxicosis in 17). Twenty-five patients subsequently developed hypothyroidism following thyrotoxicosis. The cumulative incidence of thyroid irAEs differed among 4 groups classified by the presence of TgAb/TPOAb at baseline (group 1: TgAb-(-)/TPOAb-(-), 4.6% [19/415]; group 2: TgAb-(-)/TPOAb-(+), 15.8% [9/57]; group 3: TgAb-(+)/TPOAb-(-), 42.1% [8/19]; group 4: TgAb-(+)/TPOAb-(+), 60.0% [15/25]) as follows: groups 1 vs 2-4 (P ≤ .001) and groups 2 vs 3 (P = .008) and 4 (P < .001). There were different incidences of thyrotoxicosis (groups 1-4, 3.1%, 5.3%, 31.6%, 48.0%, respectively; P < .001) in groups 1 vs 3 and 4, and groups 2 vs 3 and 4, and of hypothyroidism (groups 1-4: 2.9%, 15.8%, 31.6%, 60.0%, respectively; P < .001) in groups 1 vs 2 to 4, and groups 2 vs 4.

The risk of thyroid irAEs was affected by the pattern of TgAb and TPOAb positivity at baseline; there were high risks of thyrotoxicosis in patients with TgAb-(+) and of hypothyroidism in patients with TgAb-(+) and those with TPOAb-(+).