DNA damage in thyroid cancer patients treated with radioactive iodine in Johannesburg, South Africa

Thyroid cancer is the most common endocrine cancer globally. The National Cancer Registry has estimated the prevalence of the disease to be higher in females than in the male population with a risk of 1 in 506 females and 1 in 1035 in males in South Africa. Thyroid cancer mostly develops in the thyroid nodules. If cancerous then the malignant cells can spread to the nearby lymph nodes or by the blood vessels to other organs. The aim of the study was to investigate the correlation between ¹³¹I emitted ionizing radiation and the induced and persistent DNA damage in patients treated with radioactive iodine. Patients suffering from thyroid cancer and treated with radioactive iodine face an increased risk of secondary cancers due to potential chromosomal damage from exposure to ionising radiation. We used the cytokinesis - block micronucleus assay to assess chromosomal damage at four time points. We found that therapy induced micronuclei increased with the amount of radioactive iodine activity. There was a significant difference in the mean number of micronuclei in thyroid. Our results emphasize the need for ongoing monitoring of chromosomal damage in thyroid cancer patients to understand the long-term implications of radioactive iodine therapy. We anticipate that further research exploring the effects of treatment intervals on genetic stability and the potential risks of retreatment, may elucidate the true impact of this routinely used treatment on DNA damage, particularly in patients who may receive consecutive radioiodine therapies. Sensitivity of chromosomes to radiation is assessed by studying the induced DNA damage. The correlation between iodine radioactivity and DNA damage was assessed in our environment with limited resources. The results showed a significant increase in micronuclei following treatment, peaking at discharge before a slight decline at about six months’ time point.