Thyroid Dysfunction Induced by Radiotherapy Treatment in Patients with Breast Cancer

Breast cancer is the most common cancer and second most common cause of cancer death among US women,. External beam radiation therapy (RT) that involves the breast and regional lymph nodes, including axillary and supraclavicular (SCV) lymph nodes, has been demonstrated to decrease the risk of local recurrence and improve long-term survival in high-risk breast cancer patients . However, RT-induced toxicities to adjacent normal tissues can lead to serious morbidity in cancer survivors . The thyroid regulates the body's metabolism via producing thyroxine (T4) and triiodothyronine (T3) hormones. As the thyroid is sensitive to RT, radiation-induced thyroid disorders have been reported in cancer patients who received radiation in the cervical or SCV regions . In breast cancer patients, RT to the SCV area has been associated with a higher incidence of Hypothyriodism, particularly in younger patients This complication may be associated with radiation-induced thyroid volume reduction . Recent studies,have reported a significant decrease in thyroid volume (14-30 %) in patients with laryngeal or nasopharyngeal carcinoma (NPC), suggesting an association between HT and post-RT thyroid atrophy . Little is known about the changes of thyroid gland volume based on local thyroid gland radiation dose and its correlations with incidence of HT. Our study aim the changes in thyroid volume of breast cancer patients who received RT to the SCV nodal area, to evaluate RT-induced thyroid gland evolution based on local radiation dose. We then assessed the association between thyroid volume changes and the incidence of post-RT Hypothyrodism in breast cancer patients. the aim of the study to diagnose subclinical hypothyroidism and biochemical changes in thyroid function after radiotherapy for breast cancer