Material and Methods
Study Design and Population
This was a retrospective study. From January to December 2019, 41 patients were referred from Oncology and Pneumology to Endocrinology of The University Hospital of Pisa because of thyrotoxicosis due to anti-PD1 or anti–PD-L1 treatment. Thyrotoxicosis was defined as the finding of high levels of free thyroxine (FT4) and/or free 3,5,3'-triiodothyronine (FT3) associated with low to undetectable levels of thyrotropin (TSH). Inclusion criteria were: 1) patients 18 years or older with a cytologically/histologically confirmed type of solid cancer treated with an anti-PD1 or anti–PD-L1 drug as the first line of immunotherapy; 2) medical history unremarkable for thyroid disease; 3) FT4, FT3, and TSH in the normal range at the screening performed during the month preceding the start of immunotherapy; 4) neck ultrasound and thyroid scintigraphy performed at the onset of thyrotoxicosis; and 5) at least 6 months of follow-up. We decided to focus our study on patients treated with anti-PD1 or anti–PD-L1 drugs, which, compared to anti–CTLA-4 drugs, are currently employed more frequently and more commonly cause thyroid dysfunction. Additionally, given the different role played by the CTLA-4 and PD1/PD-L1 pathways in immune regulation, we excluded patients previously treated with anti–CTLA-4 to avoid overlapping effects of the 2 drugs. Of 41 patients with thyrotoxicosis, 17 did not match the inclusion criteria because they lacked baseline data (N = 6), neck ultrasound or thyroid scintigraphy (N = 8), or because they were being treated with levothyroxine (N = 3). Of the remaining 24 patients, 4 were excluded because they had been previously treated with an anti–CTLA-4 drug, resulting in the 20 patients featured in this particular study (Table 1). Mean age was 62 years and 65% were male. Non–small cell lung cancer was the most common type of tumor, followed by melanoma, hepatocellular carcinoma, and renal carcinoma. Seventeen patients were treated with an anti-PD1 (10 nivolumab and 7 pembrolizumab) and 3 with an anti–PD-L1 drug (2 atezolizumab and 1 durvalumab). All patients had a computed tomography (CT) scan 7 to 21 days before the screening sample, and 4 patients had an additional CT scan between the screening and the onset of thyrotoxicosis (ie, time 0). The mean time from the start of immunotherapy to the onset of thyrotoxicosis was 2.5 months, while the mean time from the administration of last iodine contrast medium was 3.4 months. The mean time of follow-up was 9.6 months and no patient stopped ICIs during follow-up. The study was conducted in accordance with the ethical principles of the Declaration of Helsinki. Data publication was approved by the local institutional review committee (Comitato Etico di Area Vasta Nord Ovest–CEAVNO). Patients were informed and gave their consent to participate in the study.
Thyroid function (FT4, FT3, and TSH) was tested at screening performed before the start of immunotherapy (baseline) and then every 14 to 21 days at each drug infusion.
Data are therefore reported at day 0 (the time of onset of thyrotoxicosis), 14 (or 21), 28, 42, 56 (or 63), 70, 84, 98 (or 105), 112, 126, 140 (or 147), 154, 168, and 182. Thyroglobulin antibodies (TgAbs) and thyroperoxidase antibodies (TPOAbs) were tested at screening and at day 0 in all patients, while thyroglobulin (Tg) and urinary iodine were tested at day 0. Thyrotropin receptor antibodies (TRAbs) were measured at time 0 in all patients and retested during follow-up in selected patients when Graves disease was suspected. Neck ultrasound and thyroid scintigraphy were performed at the onset of thyrotoxicosis. Given the absence of a conventional treatment, an antithyroid drug was started in some patients during follow-up, based on the course of thyrotoxicosis. Hypothyroidism was diagnosed on the basis of 2 consecutive findings of low FT4 associated with slightly increased TSH (4–10 mIU/L), or of a single detection of low levels of FT4 associated with high TSH (> 10 mIU/L).
Thyroid hormones and TSH were tested using immunoenzymatic assays (Ortho Clinical Diagnostics Inc). Reference ranges were 8 to 18 ng/L for FT4, 2.5 to 5.0 ng/L for FT3, and 0.4 to 4 mIU/L for TSH, respectively. Tg was measured by an immunometric assay (Access Thyroglobulin assay; Beckman Coulter Inc) (functional sensitivity 0.1 ng/mL). TgAbs were measured by an AIA-Pack 2000 TgAb-IgGs (Tosoh Corp); analytic, functional, and positive cutoffs were 6 IU/mL, 8 IU/mL, and 30 IU/mL, respectively. In this assay TgAbs interfere with Tg measurement when greater than or equal to 9.3 IU/mL. TPOAbs were checked by an AIA-Pack 2000 TPOAb (Tosoh Corp) (positive cutoff > 10 IU/mL). TRAbs were tested by enzyme-linked immunosorbent assay (ElisaRSR TRAb 3rd Generation) (positivity cutoff > 1.5 IU/mL). Urinary iodine was measured by mass spectroscopy (reference range, 100–300 μg/L).
Neck ultrasound was performed by Technos (Esaote Biomedica) with a 7.5-MHz linear transducer. Thyroid volume was calculated using the ellipsoid volume formula. According to the upper limit of normal thyroid volume estimated in the reference Italian adult population (12.1 mL in women and 16.5 mL in men, respectively), patients were divided into 2 subgroups: 1) with normal thyroid volume; and 2) with goiter.
99mTechnecium (Tc) scintiscan was performed using a dedicated γ camera with a parallel-hole collimator, 20 minutes after the intravenous administration of 3 to 5 mCi (111–185 MBq) of 99mTc-pertechnetate. The field of view extended from the salivary glands level to the upper sternum. Anterior images were obtained for 100 000 counts (or 5 minutes) with the patient sitting and neck extended, and a radioactive marker was placed on the sternal notch. According to the image obtained, patients were classified into 2 groups: 1) Sci+: with a distinct thyroid image due to uptake of technetium (Figure 1A); and 2) Sci–: with no thyroid image because of absent uptake (Figure 1B).
A, Formation of a scintigraphy image due to a normal/increased uptake of technetium (Sci+). B, Absent formation of a scintigraphy image due to an absent uptake of technetium (Sci–). In both patients neck ultrasound showed diffuse goiter.
Statistical data analysis was performed using SPSS 21 (IBM Corp). Data are presented as mean ± SD or median with interquartile range, as indicated. The Shapiro-Wilk test was used to assess normality of data distribution of continuous variables. Statistical tests used to compare groups included the t test for normally distributed variables and Mann-Whitney U tests for variables with skewed distribution. The chi-square test or the Fisher exact test was used to compare counts and frequencies between groups for categorical variables as appropriate. Pearson (R) and Spearman (ρ) correlation coefficients were used to quantify association for Gaussian and skewed continuous variables, respectively. Multivariate regression analysis was conducted to identify the independent determinants of time to remission (dependent variable) among clinical parameters (independent variables). Repeated-measures mixed-model analysis was used to assess intergroup differences in thyroid hormone concentrations over time.
J Endo Soc. 2021;5(9) © 2021 Endocrine Society