Incidence of Thyroid Function Test Abnormalities in Patients Receiving Immune‐Checkpoint Inhibitors for Cancer Treatment

AbstractBackground.With the advent of immune‐checkpoint inhibitor (ICI) therapy (anti‐CTLA‐4, anti‐PD‐1), immune‐related adverse events such as thyroid function test abnormalities (TFTAs) are common, with a reported incidence range of 2%–15% depending upon the ICI used. The aim of this study is to describe the incidence of TFTAs retrospectively in patients who received ICI therapy.Methods.A total of 285 patients were reviewed (178 male, 107 female; 16–94 years of age), of whom 218 had no baseline TFTAs, 61 had baseline TFTAs, and 6 had a history of thyroidectomy (excluded). At least one dose of ipilimumab and/or nivolumab or pembrolizumab was administered. Post‐ICI therapy TFTAs were classified according to standard definitions of thyroid conditions when possible.Results.A total of 35% (76/218) patients had new‐onset TFTAs on ICI therapy. Of note, 70.5% (43/61) had baseline TFTAs that were exacerbated by ICI therapy. The median times to new‐onset or exacerbated baseline TFTA were 46 and 33 days, respectively. Of note, 64.5% (20/31) of patients on both ipilimumab and nivolumab had new‐onset TFTAs, compared with 31.3% (15/48) on ipilimumab, 31.5% (28/89) on nivolumab, and 26% (13/50) on pembrolizumab.Conclusion.The incidence of TFTAs with ICI therapy was higher than previously reported. Patients with baseline TFTAs and/or who were receiving ipilimumab and nivolumab combination therapy had a higher incidence of TFTAs than patients receiving single‐agent ICI therapy. We recommend more frequent evaluation of thyroid function in the first 8 weeks, especially in patients with baseline TFTAs.Implications for Practice.Increased use of immune‐checkpoint inhibitors in cancer treatment has highlighted the importance of monitoring for and treating immune‐related adverse events. This study was conducted to assess the incidence of thyroid function test abnormalities retrospectively in patients with cancer on immune‐checkpoint inhibitors, which is not known exactly. This study is unique in that it included patients with a variety of histologic subtypes of cancer and also followed the clinical course of patients with baseline thyroid function test abnormalities. This study can help make oncologists aware that the incidence of thyroid function test abnormalities is higher than anticipated. Early identification and timely treatment can help ameliorate symptoms for patients and improve their overall quality of life.

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