The incidence rate of renal cell carcinoma (RCC) has gradually increased worldwide over the past decade. Targeted therapy is the primary method for treating metastatic renal cell carcinoma (mRCC), and the development of thyroid dysfunction is one of the most common adverse reactions of this treatment. Therefore, this study aimed to assess the value of sonography in monitoring the morphology and functions of the thyroid in metastatic renal cell carcinoma patients treated with targeted drugs.
In total, 37 patients from September 2016 to April 2019 with clinically confirmed mRCC that were treated with targeted drugs (19 with sunitinib and 18 with sorafenib) were enrolled in this study. The enrolled patients were divided into the hypothyroidism group and the non-hypothyroidism groups according to the changes in the serum concentration of the thyroid-stimulating hormone (TSH) during the treatment period. The serum concentrations of free triiodothyronine (FT3), free thyroxine (FT4), and TSH were measured by the Roche method before and after treatment. Simultaneously, the major axis, transverse diameter, and anteroposterior diameter of the bilateral lobes and isthmus of the thyroid gland were measured by ultrasound, and every thyroid volume was calculated. The changes in the thyroid volume, the thyroid volume change rate, and the homochronous serum concentration of TSH, FT3, FT4 in the hypothyroidism group, and the non-hypothyroidism group were then compared to assess the value of using sonography for monitoring the changes of thyroid morphology and functions.
In total, 20 patients had hypothyroidism (hypothyroidism group), while 17 patients did not have hypothyroidism (non-hypothyroidism group). The thyroid volumes in both groups decreased gradually after targeted therapy. In the 1st, 2nd, 3rd, 4th, 5th, 6th, 9th, and 12th month after the treatment, the rate of change in thyroid volume in the hypothyroidism group (n=20) was 0.84 (0.47)%, 3.36 (1.34)%, 6.95 (1.42)%, 8.57 (1.66)%, 9.15 (0.55)%, 10.40 (1.12)%, 13.30 (1.53)%, and 14.15 (1.85)%, respectively. In the non-hypothyroidism group (n=17), the thyroid volume change rates were 0.25 (0.11)%, 3.00 (1.81)%, 3.9 (0.75)%, 5.09 (1.81)%, 6.72 (1.81)%, 6.90 (1.35)%, 9.90 (1.35)%, and 10.60 (1.79)%, respectively. There were significant differences in the rate of change in thyroid volume between the hypothyroidism and non-hypothyroidism group after treatment (F =490.804, P=0.000). When the thyroid volume change rate reached 8.5%, the sensitivity, specificity, and accuracy of using ultrasound in evaluating the occurrence of hypothyroidism were 70.3%, 94.1%, and 75.0%, respectively. The area under the curve (AUC) of the receiver operating characteristic curve (ROC) was 0.845.
Using ultrasound as a tool can precisely detect the reduction of thyroid volume induced by targeted drugs used in mRCC therapy. For mRCC patients treated with targeted drugs, the degree of thyroid volume reduction in patients with hypothyroidism is higher than those without hypothyroidism. Furthermore, the rate of thyroid volume change in patients with mRCC can indirectly monitor the changes in thyroid function after a targeted treatment in these patients. The degree of thyroid volume reduction of 8.5% was relatively sensitive, specific, and accurate for the diagnosis of hypothyroidism.

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