Title: Estimation of Effective Half-Life of I-131 in Differentiated Thyroid Cancer Patients in a Tertiary Care Hospital in India: A Retrospective Study
Authors: Amit Sharma, Sandeep K Issac, Anil Kumar Pandey, Brig MS Chauhan, Brig MJ Jacob, Col AG Pandit, Sumit Agarwal, Anurag Jain8, IP Dubey, Braj Kishore, Awadhesh Tiwari, Surya Prakash
DOI: https://dx.doi.org/10.18535/jmscr/v5i3.76
Abstract
Introduction: Patients having differentiated thyroid cancer (DTC) undergo radio-iodine (I-131) therapy to ablate normal residual thyroid tissue after surgery and this is known to reduce rates of death and recurrence. The objective of the study was to assess the effective half-life of I-131 clearance in differentiated thyroid cancer patients.
Material and Methods: The exposure rate (mR/hr) of ninety one patients treated for remnant thyroid ablation with I-131 were analyzed. These measurements were taken immediately after dose administration at a distance of one meter from the patient at the level of abdomen and then on subsequent days at the level of maximum activity, till the patient is discharged under recommended regulatory limits (<50uSv/hr, 5mR/hr).
Results: We found the effective clearance of I-131 as bi-exponential and the t-significant amount (65%) of activity was excreted through the urine within 20 hrs. In the group of patients administered 3.7GBq (100mCi) I-131, the first phase clearance was found to be at 13.72 hour and final phase clearance was at 18.91 hr (range 8.84- 177.42hr). We also found the differences in effective half life in two groups viz 3.7GBq and 5.55 GBq.
Conclusion: The mean effective half-life in the 3.7GBq (100mCi) group was 13.72 hrs at initial phase and 18.91 hrs at the final phase. The data generated in this study will be useful in formulating guidelines for the staff and the person coming close proximity to the patients during and after the high dose I-131 therapy.
Keywords: effective half-life, differentiated thyroid cancer and remnant ablation.
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