Ultrasound evaluation of changes in thyroid volume and selected parameters on Doppler examination in radically irradiated patients with primary cancers of the head and neck region - preliminary report

Introduction: Implementation of even the most advanced radiotherapy techniques is still associated with a risk of damaging healthy tissues and organs by ionizing radiation. Structural and functional abnormalities of the thyroid gland have been reported in patients after radiotherapy administered for head and neck cancers (HNC). Aim: Ultrasound evaluation of changes in thyroid volume, characteristics of blood flow in the right inferior thyroid artery (ITA) and vascular invasion (VI) of the thyroid gland in patients radically irradiated due to primary HNC. Material and methods: The study group consisted of 20 patients who underwent ultrasound examinations at three time points: prior to commencing radiotherapy (I), in the first week after completion of radiotherapy (II) and after another 3–6 months (III). Results: The mean radiation dose absorbed by the thyroid gland was 54.95 6.95 Gy. The mean thyroid volume measured at the first time point was 17.14 (13.74–23.43) cm3 and this result turned out to be higher as compared to measurements obtained in the second and third examinations: 15.92 (12.51–20.35) cm3 with p<0.001; 15.01 (11.16–18.92) cm3 with p<0.001, respectively. Thyroid volume from the second examination was also greater than in the third examination (p<0.001). Evaluation conducted at time point II showed an increase in the following vascular flow parameters: peak systolic velocity (PSV), pulsatility index (PI) and resistivity index (RI) measured in the ITA, as well as an increase in thyroid VI in comparison to results from time point I. Furthermore, a decrease of the above-mentioned values was observed at time point III as compared to time point II. However, the ultrasound vascular characteristics measured in the ITA and VI of the thyroid gland were still higher on examination III when compared to the initial values. Conclusions: We have observed that radiotherapy leads to a decrease in thyroid volume, which is found to be progressing for at least 3–6 months after treatment completion. Post-radiotherapy changes in vascular parameters of the ITA and VI value measured on Doppler ultrasound partially resolve within 3–6 months after the end of radiation treatment.