Radioiodine Treatment and Thyroid Hormone Suppression Therapy for Differentiated Thyroid Carcinoma: Adverse Effects Support the Trend toward Less Aggressive Treatment for Low-Risk Patients

Abstract

Over the past decades, the incidence of differentiated thyroid carcinoma (DTC) has steadily increased, with especially a growing number of low-risk patients. Whereas DTC used to be treated rather aggressively, it is now acknowledged that aggressive treatment does not affect outcome for low-risk patients and that it can induce adverse effects. In this review an overview of the most clinically relevant adverse effects of radioiodine treatment and thyroid hormone suppression therapy (THST) is presented, and the trend toward less aggressive treatment for low-risk patients is outlined. Salivary gland dysfunction occurs in roughly 30% of patients, and is probably due to the concentration of radioiodine in the salivary glands by the sodium/iodide symporter. Beta radiation from radioiodine can result in sialoadenitis and eventually fibrosis and loss of salivary function. Furthermore, patients can experience bone marrow dysfunction following radioiodine treatment. Although this is in general subclinical and transient, patients that receive very high cumulative radioiodine doses may be at risk for more severe bone marrow dysfunction. THST can induce adverse cardiovascular effects in patients with DTC, such as diastolic and systolic dysfunction, and also adverse vascular and prothrombotic effects have been described. Finally, the effects of THST on bone formation and resorption are outlined; especially postmenopausal women with DTC on THST seem to be at risk of bone loss. In the past years, advances have been made in preventing low-risk patients from being overtreated. Improved biomarkers are still needed to further optimize risk stratification and personalize medicine.

Long‐term cardiovascular morbidity and mortality in patients treated for differentiated thyroid cancer

“…Diagnosis of small low‐risk tumours may expose the patients to aggressive cancer treatment, which may have unfavourable long‐term effects . Thyroid hormone suppression therapy (THST) by levothyroxine has been traditionally used as a treatment of thyroid cancer to improve the outcome, but recently the necessity and safety of this treatment in low‐risk patients have been questioned . There are concerns about the long‐term cardiovascular effects of THST‐induced iatrogenic thyrotoxicosis, as the risks of endogenous hyperthyroidism are well known …”

Effects of Radioiodine Treatment on Salivary Gland Function in Patients with Differentiated Thyroid Carcinoma: A Prospective Study

“…Patients with DTC have a favorable survival, which is presumably due to the relative indolent nature of the disease combined with an effective treatment consisting of a (near)-total thyroidectomy, radioiodine ( 131 I) treatment, and thyroid hormone suppression therapy. Adverse effects of treatment are increasingly being recognized, among them radioiodine-induced salivary gland damage (2).…”

“…These processes can lead to obstruction of the ductal system, causing an inflammatory response in the secretory tissue (sialoadenitis), and glandular degeneration (5). Moreover, salivary gland stem cells, which have been proposed to mainly reside in the excretory ducts (6), may be affected because of the exposure to b-radiation resulting in a reduced regenerative potential (2).…”

Successful Treatment of Differentiated Thyroid Carcinoma with Transaxillary Robotic Surgery and Radioiodine: The First European Experience

“…Furthermore, the local practice of RAI treatment changed recently during this period concerning indications (less indication in low-risk patients), iodine dose (more ablative than adjuvant dose) and type of preparation used (more rhTSH). Nowadays, fewer treatments are required, in particular for low-risk patients [18]. …”