Improved survival in patients with thyroid function test abnormalities secondary to immune-checkpoint inhibitors

Immune-checkpoint inhibitors (ICI) are monoclonal antibodies which target molecules to enhance antitumor response. Several adverse events have been described and the major ICI-related endocrinopathies are thyroid dysfunction and hypophysitis. Its occurrence has been associated with improved outcomes, but it is still to be proven. We performed a retrospective study of patients treated with ICI between 2014 and 2019 at an oncologic center to characterize thyroid function test abnormalities (TFTA) and to evaluate clinical outcomes. We excluded patients without regular monitoring of thyroid function, with previous thyroid or pituitary disease, previous head/neck radiotherapy and who performed only one ICI cycle. We included 161 of 205 patients treated with pembrolizumab, nivolumab or ipilimumab for several neoplasms, with a median duration of 18.9 weeks (9.1-42.6) of ICI treatment and 49.4 weeks (26.5-75.8) of follow-up. New-onset TFTA was diagnosed in 18% of patients (n = 29), in median at 10.6 weeks (6.1-31.1) of ICI therapy. On the whole, 8.7% had primary hypothyroidism, 4.3% central hypothyroidism, 2.5% biphasic thyroiditis and 2.5% thyrotoxicosis. Patients who experienced primary or central thyroid dysfunction had a significantly improved overall response rate (58.6% vs 34.2%, p = 0.015) and overall survival (3.27 vs 1.76 years, p = 0.030), compared to the control group. The risk of mortality was two times higher for control group (adjusted HR = 2.43, 95% CI 1.13-5.23, p = 0.023). This study recognizes that primary and central thyroid dysfunction can be a predictive clinical biomarker of a better response to ICI across several neoplasms.