Radiation Dose-rate Reduction Pattern in Well-differentiated Thyroid Cancer Treated with I-131

Area of Science:

• Nuclear Medicine
• Oncology
• Radiological Physics

Background:

• Well-differentiated thyroid cancer (WDTC) is frequently treated with radioactive iodine (I-131) therapy.
• Patient management involves monitoring radiation dose rates for safe discharge.
• Understanding dose rate reduction patterns is crucial for optimizing treatment protocols.

Purpose of the Study:

• To investigate the dose rate reduction patterns following single and multiple I-131 therapies in WDTC patients.
• To compare the kinetics of dose reduction between initial and subsequent radioiodine treatments.

Main Methods:

• An analytical series study was conducted from December 2006 to December 2013.
• Ninety-three WDTC patients (167 therapies) received I-131 inpatient treatment.
• Patients were categorized into single (n=54) and multiple (n=39) therapy groups, with doses ranging from 70-150 mCi and 80-250 mCi, respectively. T-test was used for statistical analysis.

Main Results:

• The study included 68 females and 25 males, aged 15-80 years (mean 36).
• Following the first I-131 therapy, 63% of patients were discharged within 48 hours.
• Patients receiving second or subsequent therapies were discharged significantly earlier, with only 5% remaining hospitalized beyond 48 hours, achieving a discharge dose rate of ≤25 µSv/hour.

Conclusions:

• Subsequent radioiodine (RAI) therapies in WDTC patients demonstrate a more rapid dose rate reduction compared to initial treatments.
• This accelerated reduction facilitates earlier patient discharge after multiple RAI administrations.
• Findings support the refinement of discharge criteria based on the number of RAI therapies received.