To compare the effect of conventional radiotherapy versus concurrent chemoradiotherapy on the thyroid gland after external beam radiotherapy in head-and-neck carcinoma

Abstract

Introduction: Radiotherapy-induced hypothyroidism has remained underestimated and under reported ailment, because of noninclusion of routine assessment of thyroid function test in baseline workup and during follow-up protocol, which results in failure to detect and treat a reversible cause of morbidity in significant proportion of surviving patients. Greater magnitude and duration of thyroid-stimulating hormone elevation increase the probability of progression to clinical hypothyroidism and therefore increase the potential benefit of treatment of subclinical hypothyroidism. Hence, recognizing subclinical hypothyroidism at an early stage can prevent clinical hypothyroidism and its associated morbidities. Aims and Objectives: The aim of the present prospective study was to evaluate the functional and anatomical changes in thyroid glands in patients with head-and-neck cancer treated with conventional radiotherapy (external beam radiotherapy) and concurrent chemoradiotherapy and to assess the necessity of inclusion of routine thyroid function test in the workup and follow-up protocol of these patients. Materials and Methods: A total of 98 patients were randomly allocated in two arms. In arm I, 50 patients received concurrent chemoradiotherapy and in arm II, 48 patients underwent radical conventional radiotherapy alone. Baseline thyroid function test and ultrasonography of neck along with thoroughly clinical evaluation were done for every patient and these investigations were repeated in the middle of radiotherapy treatment (after 17 #), at the end of radiotherapy treatment, 3 months after completion of radiotherapy, and after that, at every 3rd-month follow-up to determine late changes in thyroid function test and echotexture. Results: In arm I, total 60% patients developed acute hyperthyroidism while in arm II, 68.75% patients developed acute hyperthyroidism. A total of 18.36% patients were found to have subclinical hypothyroidism. At the 9th month of follow-up, 55 out of 98 patients (56.12%) developed hypothyroidism. Among 55 patients, 37 were having clinical hypothyroidism while 18 patients were having subclinical hypothyroidism (P ≤ 0.0001). Maximum number of patients, i.e. 26/98 (47.27%) developing hypothyroidism were between 51 and 60 years of age group. Addition of surgery and chemotherapy had shown no difference in thyroid dysfunction. Patients with clinical hypothyroidism required medical management while patients with subclinical hypothyroidism were kept on close monitoring. Conclusion: Recognizing hypothyroidism (clinical or subclinical) early and treating it timely can prevent associated complications which are often ignored. Hence, thyroid function tests should be done routinely that is before starting of radiotherapy, on completion of radiotherapy, and during follow-up as well.