Assessment of Low Versus High Doses of Radioiodine in Differentiated Thyroid Carcinoma Using Gamma Camera

Abstract

Thyroid cancer is a type of cancer that starts in the thyroid gland. The thyroid makes hormones that help regulate your metabolism, heart rate, blood pressure, and body temperature. Differentiated thyroid cancer (DTC) is a type of thyroid cancer where the cancer cells, when viewed under a microscope, look similar to normal thyroid cells. It's the most common type of thyroid cancer, with the majority of cases being either papillary or follicular thyroid cancer. DTC is generally slow-growing and treatable, with good prognosis in most cases. The primary objective of this study is to investigate the effects of low and high doses of radioactive iodine in the treatment of differentiated thyroid cancer (DTC). To achieve this goal, 100 adult patients with thyroid cancer who underwent total or near-total thyroidectomy received either 1.1 GBq (30 mCi) or 3.7 GBq (100 mCi) of radioactive iodine (I-131). The patients were classified as low or intermediate risk based on the American Thyroid Association (ATA) criteria. In Saudi Arabia, data were retrospectively collected from multiple nuclear medicine centers, with an equal number of male and female patients selected, having an average age of 40.72 ± 11.49 years. After radioactive iodine therapy (RIT), thyroglobulin (Tg) levels were below 10 ng/mL in both groups, with 72% in the high-dose group and 66% in the low-dose group. No significant therapeutic difference was observed in treatment efficacy for individuals classified as low and intermediate risk. Statistics indicated that the success rate of RIT ablation with low doses was nearly equivalent to that of high-dose ablation (82%). This research demonstrated that both low and high-dose ablation effectively reduce Tg levels and achieve successful ablation. Therefore, low-dose RIT ablation is recommended over high-dose ablation for patients with low or intermediate-risk thyroid cancer. The secondary objective of this research was to investigate the relationship between age (45 years) as a predictive factor and Tumor, Node, Metastasis (TNM) staging in thyroid cancer patients who underwent radioactive iodine treatment six months prior to staging. This peer study included 100 thyroid cancer patients, 70% female and 30% male, who underwent thyroid surgery. Patient data were categorized into two groups: the mean age of the first group (G1 ≥ 45 years) was 52.641 ± 65.895 years, while the mean age of the second group (G2 <45 years) was 31.037 ± 6.193 years, according to TNM stages. RIT risk factors were classified as high, low, or very low. The p-values for T-stage and N-stage were 0.7338 and 0.9668, respectively.

The data indicated no statistically significant association between G1 and G2 in individuals with direct thyroid cancer during the T and N stages. However, the M-stage with a p-value of 0.0026 at M0 indicated a statistically significant difference between the two groups. Age at diagnosis is one of the most reliable indicators for direct breast cancer staging. Alongside conventional risk indicators (tumor size, lymph node involvement, distant metastasis, and treatment), an age threshold of 45 years compared to 55 years or older may play a more modest role in stratifying cancer-specific risk and mortality in cases of DTC.