Investigating the Release Criteria for Thyroid Cancer Patients Receiving High-Dose I-131 Radiation Therapy

摘要

Background: We retrospectively investigated the change of radiation exposure rate of thyroid cancer patients who are treated with high-dose I-131. Clinical factors which may influence dose rate were also evaluated. Methods: During the hospitalization, we used Ludlum Model 375 monitor with probe of Ludlum Model 133-2 to measure the dosimetry (μSv/hr) of patients. Dose rates were assessed at , 6, 16, 2, 27, and 40 hr. A standardized distance of 1 m was maintained between the patients and the detector. Results: A total of 582 thyroid cancer patients (922 hospitalizations) were evaluated. The time required for the dose rate dropping to 100, 70, or 50 μSv/hr were 6.4 ± 4.1 hr (range: 0.1 to 26.3), 12.3 ± 5.3 hr (range: 0.3 to 31.2), or 17.8 ± 5.7 hr (range: 2.9 to 37.1), respectively. All patients had their dose below 70 μSv/hr at 36 hr post administration of I-131. Patients with elder age (p = 0.013), male gender (p < 0.001), hospitalization due to ablation or adjuvant therapy (p = 0.002) or use of Thyrogen (p < 0.001) had a longer half-life of measured radiation dose. In addition, age, sex, indication for therapy, dose of administered I-13, and use of Thyrogen significantly influenced the time to reach 70 μSv/hr. Conclusion: This retrospective study indicated that for patients receiving high-dose of I-13, it takes about 36 hours for the radiation down to 70 μSv/hr. Age, sex, indication for therapy, administered dose of I-13, and use of Thyrogen significantly influenced the decreasing rate of radiation.