Pattern and Determinants of Early Thyroid Hormone Profile Changes Following Radiotherapy for Head and Neck Cancers at the Kenyatta National Hospital.

Abstract

Background: Head and neck cancers are ranked as the 3rd commonest cancers globally. Majority of the cancers (60%) are treated with radiotherapy. The thyroid gland is one of the organs at risk of damage due to the effects of neck irradiation. Thyroid gland dysfunction can occur early or late and increase the morbidity. Objective: This study evaluated the pattern and determinants of early changes in thyroid hormone profiles following radiotherapy for head and neck cancers at the Kenyatta National Hospital. Methodology: This was a prospective observational study of 50 patients with head and neck cancers who were treated with radiotherapy at the Kenyatta national hospital. Convenience sampling technique was used to recruit patients. Data collection tool captured demographics, clinical and disease characteristics, treatment modality, pre-treatment and three months post radiotherapy thyroid function test results. Data management and analysis: Data was expressed as means and standard deviations. Analysis of variance was used to determine type of thyroid dysfunction at three months post radiotherapy with a p value of <0.05 being significant. Exact fisher test was used to correlate variables and development of thyroid dysfunction with a p value of < 0.05 being significant. Results: Results of fifty patients was analysed which constituted 31(62%) males, and 19 (38%)females. The mean age was 52.4±16.6 years with an age range of 18-82 years. Thyroid dysfunction occurred in 2(4%) patients before commencement of radiotherapy. Fifteen patients (30%) had thyroid dysfunction at three months after completion of radiotherapy. This comprised 6(12%) patients with subclinical hypothyroidism, 6(12%) patients with clinical hypothyroidism,1(2%) patient with subclinical hyperthyroidism ,2(4%) patients with clinical hyperthyroidism. There was significant change in FT3(2.94±0.72) to (2.96±0.84) after radiotherapy with a p value of <0.04. Chemotherapy and the degree of differentiation of tumour influenced development of thyroid dysfunction with a p value of < 0.03 and 0.04 respectively. Age, gender, cancer subsite, TNM stage, radiotherapy machine type, duration of treatment had no-significant influence on development of thyroid dysfunction with a p value > 0.05. Conclusion: The thyroid gland is affected by radiotherapy during treatment of head and neck cancers. Thyroid hormones were found to increase at three months. Chemotherapy and degree of differentiation of the tumour were the key determinants in development of thyroid dysfunction. We therefore recommend long term follow up of these patients to see if the patterns of thyroid profile would remain the same or change. We also recommend further studies with larger sample size to see the trends in thyroid hormone changes. We also recommend routine thyroid functions tests pre and post radiotherapy.