Thyroid dysfunction during PD-1 inhibitor treatment in patients with cancer: Incidence and association with progression-free survival

The use of programmed cell death-1 (PD-1) inhibitors has recently been approved in China. As a consequence, the identification of relevant prognostic markers that can assess the efficacy of these compounds is required. Therefore, the present study aimed to explore the incidence of thyroid dysfunction and its ability to predict progression-free survival (PFS) in Chinese patients with cancer who received PD-1 inhibitor treatment. Data from 72 patients with cancer who received treatment with PD-1 inhibitors alone or in combination with chemotherapy or targeted drugs were analyzed. Moreover, the expression levels of free triiodothyronine, thyroxine, and thyrotropin during treatment were assessed to evaluate thyroid dysfunction. A total of 26 (36.1%) patients who had received PD-1 inhibitors developed thyroid dysfunction. Specifically, the incidence of thyroid dysfunction was 35.6% in patients with lung cancer, 25.0% in patients with malignant melanoma, and 46.7% in patients with other types of cancer. In addition, the median PFS was 7.0 (95% confidence interval, 4.9-9.1) months, whereas the 1- and 2-year PFS rates were 35.1 and 26.2%, respectively. Generally, patients with thyroid dysfunction exhibited longer PFS compared with those without thyroid dysfunction (P=0.001). Subgroup analyses were subsequently performed, which demonstrated that thyroid dysfunction was associated with longer PFS in patients with malignant melanoma (P=0.039) and other types of cancer (P=0.002), but not in those with lung cancer (P=0.083). These findings were noted in patients who received PD-1 inhibitor monotherapy (P=0.003), but not PD-1 inhibitor plus chemotherapy (P=0.172) or PD-1 inhibitor plus targeted therapy (P=0.582). Finally, thyroid dysfunction [P=0.001; hazard ratio (HR)=0.260] and PD-1 inhibitor monotherapy (P=0.015; HR=2.231) were identified as independent factors that could predict PFS. In conclusion, the present study demonstrated that thyroid dysfunction during PD-1 inhibitor treatment could be used as a potential marker for the prognosis of favorable PFS in patients with cancer.