From the Guidelines
For a patient with 14% radioactive iodine uptake, the recommended I-131 dose is 50 mCi (1850 MBq), as this dose has been shown to be as effective as 100 mCi (3700 MBq) in achieving successful ablation, while reducing radiation exposure to the whole body 1. This dose recommendation is based on a recent randomized prospective study that demonstrated the efficacy and safety of using a lower dose of 131 I in patients prepared with rhTSH, even in the presence of lymph node metastases 1. The use of rhTSH for preparation for radioiodine ablation has been approved in Europe and the USA, and has been shown to be highly effective and safe, with a rate of successful ablation similar to that obtained with LT4 withdrawal 1. When considering the treatment of patients with differentiated thyroid cancer, it is essential to weigh the benefits and risks of radioiodine ablation, taking into account factors such as tumor features, patient-related factors, and health-care setting 1. The goal of treatment is to achieve a euthyroid or controlled hypothyroid state, with the latter being manageable with thyroid hormone replacement therapy if needed. Some key considerations for the treatment of patients with 14% radioactive iodine uptake include:
- The patient's specific clinical factors, such as gland size, severity of disease, and age
- The use of rhTSH for preparation for radioiodine ablation, which has been shown to be highly effective and safe
- The importance of follow-up thyroid function tests to monitor effectiveness and adjust treatment as needed
- The need to balance the benefits and risks of radioiodine ablation, taking into account individual patient factors and health-care setting.
From the Research
I-131 Dose Calculation
To determine the recommended I-131 dose for a patient with 14% radioactive iodine uptake, we need to consider the studies that provide information on I-131 dosing.
- The study 2 mentions that the I-131 treatment was given as a single dose in 81 patients, 2 doses in 38, and 3 to 5 doses in 11, with a median dose of 370 MBq.
- The study 3 presents the results of treatment with 131I in a cohort of 119 patients diagnosed with toxic multinodular goiter, using a fixed dose of 555 MBq.
- The study 4 evaluated the long-term results of two schedules of treatment for toxic multinodular goitre with radioiodine therapy (I 131), with one group receiving low doses and the other group receiving calculated high doses adjusted for thyroid weight and radioiodine uptake.
- The study 5 determined the effect of a standard 15 mCi dose of 131I on the thyroid function of 25 patients from an endemic goiter region with toxic multinodular goiter.
Recommended Dose
Based on the provided studies, there is no specific formula or guideline for calculating the I-131 dose based on the percentage of radioactive iodine uptake. However, the studies suggest that a fixed dose or a dose adjusted for thyroid weight and radioiodine uptake can be effective in treating toxic multinodular goiter.
- The study 2 used a dose of 3.7 MBq/g thyroid tissue corrected to a 100% 24-hour 131I uptake.
- The study 4 used a dose of 0.5-1 mu ci/g adjusted for thyroid weight and radioiodine uptake.
- The study 5 used a standard dose of 15 mCi.
It is essential to note that the optimal I-131 dose may vary depending on individual patient factors, such as thyroid size, radioiodine uptake, and underlying health conditions. Therefore, the recommended dose should be determined on a case-by-case basis, taking into account the specific characteristics of the patient and the treating physician's expertise 2, 3, 4, 5.