Management of 131I therapy for thyroid cancer: cumulative dose from in-patients, discharge planning and personnel requirements

An Evaluation of Deviation from the International Atomic Energy Agency-International Commission on Radiological Protection Proposed Equation for Calculation of Radiation Dose Rate Emanating from the Patients with Differentiated Thyroid Cancer Undergoing Radioiodine (I-131) Therapy

The main purpose of this study was to investigate dose rate emanating from patients treated with ¹³¹I to evaluate which of the theoretical formulas, inverse-square law (ISL) and International Atomic Energy Agency-International Commission on Radiological Protection (IAEA-ICRP) suggested equation, can provide a sufficiently close approximation of the measured dose rate. Measurements were performed based on the IAEA safety report No. 63 method at 0, 12, 24, and 48 h after administration of radioiodine at a distance of 1 m for 69 patients and for the rest of 67 patients, dose rate was measured at 2, 4, 24, and 48 h at a distance of 2 m. Results revealed that the ISL formula gained better approximation of measured dose rates than the IAEA-ICRP equation with the lesser error. The ISL formula is still more reliable than the novel method of dose calculation in the vicinity of patients. This finding reminded us the prime importance of distance as a radiation protection principle.

Radiation Safety Precautions in (131)I Therapy of Graves' Disease Based on Actual Biokinetic Measurements

CONTEXT

Radiation protection is an integral part of targeted radionuclide therapy. How to offer rational radiation precautions to patients with Graves' disease (GD) undergoing (131)I therapy is still a matter of ongoing discussions.

OBJECTIVE

The objective of the study was to formulate radiation precautions for GD patients undergoing (131)I therapy through actual biokinetic measurements for a particular population of patients.

DESIGN

This was a prospective study.

SETTING

The study was conducted at a university hospital.

PATIENTS

From January 2009 through January 2012, consecutive GD patients prepared for (131)I therapy were prospectively recruited.

MAIN OUTCOME MEASURES

Pretherapy thyroid radioiodine uptake and uptake ratio (4 to 24 h radioiodine uptake) were measured. Serial whole-body dose-rate measurements after therapy were performed to deduce (131)I whole-body retention. Calculations based on deduced whole-body retention and measured thyroid radioiodine biokinetics were derived to determine the thyroidal and extrathyroidal compartment uptake fractions and effective half-lives. Precaution times necessary to avoid close contact with family members and the general public were derived from these parameters and regulatory dose limits.

RESULTS

A total of 72 patients were eligible for the analysis. A high interpatient variability in (131)I biokinetics was observed: the mean peaking (131)I uptake (±1 SD) in the thyroid was 68% (±19%), and the range was 18%-89%; the mean effective (131)I half-life (±1 SD) in the remainder of the body was 5.1 (±0.9) hours (range 3.5-7.2 h). The mean measured initial dose rate (±1 SD) at 1.0 m after (131)I administration was 0.039 (±0.003) μSv·h(-1) · MBq(-1) (range 0.017-0.055 μSv·h(-1) · MBq(-1)). The 0.3:1.0 m initial dose rate ranged from 2.9 to 7.1, which was greatly lower than the projected ratio of 11.1 by the inverse square law approximation. On the basis of the measured radioiodine biokinetics and dose rates, detailed instructions were provided to limit nearby individuals' exposure.

CONCLUSION

The use of actual biokinetic measurements may remove the effect of variability errors associated with general default assumptions about the (131)I biokinetics in GD patients. The marked variability in (131)I biokinetics among GD patients reinforces the need for patient-specific iodine biokinetic measurements for radiation safety precautions.

I-131 remnant ablation after thyroidectomy induced hepatotoxicity in a case of thyroid cancer

Background

Radioactive iodine (I-131) is routinely used for the treatment of differentiated thyroid cancer following surgery. Drug-induced liver injury (DILI) is a leading cause of acute liver failure. Here we reported a rare case of diffuse hepatic uptake (DHU) of radioactive iodine (I-131) induced hepatotoxicity in patient with I-131 ablation therapy after thyroidectomy.

Case presentation

A 57-year-old woman was admitted due to jaundice, itching and dark urine with abnormally elevated liver function. She has performed thyroidectomy followed by 100mci radioactive I-131 ablation therapy 21 days ago. The basic hepatic protection could not efficiently prevent disease progression. The patient was further treated with methylprednisolone, the bilirubin and alanin aminotransferase were finally lowered back to normal in the follow-up visit.

Conclusion

To the best of our knowledge, this is the rare description of DILI complications in thyroidectomy patient due to I-131 ablation therapy. The patient responds to glucocorticoid therapy well, but not basic hepatic protection treatment. Even though this is only a single case, it reminds physicians make DILI in early consideration when patient present liver injury after I-131 ablation therapy.

Thyroid cancer: radiation safety precautions in 131I therapy based on actual biokinetic measurements

PURPOSE

To formulate radiation precautions for patients with thyroid cancer who are undergoing thyroid hormone withdrawal-induced hypothyroidism and iodine 131 ((131)I) therapy through actual biokinetic measurements.

MATERIALS AND METHODS

Informed consent and institutional review board approval were obtained. From October 2008 to December 2011, consecutive patients with differentiated thyroid cancer who had been prepared for (131)I ablation treatment or (131)I treatment for metastatic disease during follow-up were prospectively recruited. Calculations based on deduced whole-body retention and measured iodine biokinetics in thyroidal tissue were derived to determine the thyroidal and extrathyroidal compartment uptake fractions and effective half-lives. Precaution times necessary to avoid close contact with family members and the general public were derived from these parameters and regulatory dose limits.

RESULTS

Seventy-seven patients (36 with ablation treatments, 41 with follow-up treatments) were eligible for the analysis. Actual dose rates from patients after therapeutic (131)I administration were greatly lower than those described in the American Thyroid Association (ATA) and Nuclear Regulatory Commission (NRC) models: The mean initial dose rate at 0.3 m for patients with ablation treatment was only 28% (0.183/0.655 µSv/h/MBq) ± 2.9 (standard deviation) (range, 12.1%-38.3%) and 36% (0.183/0.511 µSv/h/MBq) ± 3.7 (range, 15.5%-49.1%) of that described in the NRC and ATA models, respectively; the equivalent values for patients with follow-up treatment were only 30% (0.195/0.655 µSv/h/MBq) ± 3.5 (range, 12.5%-45.3%) and 38% (0.195/0.511 µSv/h/MBq) ± 4.5 (range, 16.0%-58.1%), respectively. The actual mean effective (131)I half-life in the thyroid remnant tissue was greatly lower than that described in the ATA and NRC models: 47.6 versus 175.2 hours.

CONCLUSION

On the basis of the current dose limits, typically administered activities of 3.7 GBq to a patient with ablation treatment or 7.4 GBq to a patient with follow-up treatment required 3 days of sleeping apart for keeping the doses to pregnant women and children below 1 mSv. No precautions were required for non-cosleeping nonpregnant adult family members.

The efficacy of patient-dependent practices on exposure rate in patients undergoing iodine-131 ablation

The authors investigated the efficacy of the patient-dependent practices (micturition, defecation, and taking a shower) after I ablation therapy in patients with thyroid cancer. Exposure rates were measured from a 1-m distance at 2, 4, and 24 h after the I administration. The comparisons for 2-4 h and 2-24 h time intervals were carried out among the patients with good and poor compliance, according to the relative amount of the patient-dependent practices, over mean values calculated for an effective half-life (h) or exposure rate decline ratio (%). In the 2-4 h interval, the mean values for good versus poor compliance were found to be: 4.16 h versus 8.14 h and 31% versus 17% in micturition; 5.70 h versus 6.84 h and 26% versus 21% in defecation; and 6.68 h versus 5.69 h and 24% versus 24% in taking a shower. Among patients with good versus poor compliance during a 2-24 h interval, the mean values were: 11.63 h versus 16.62 h and 74% versus 61% in micturition; 12.75 h versus 15.88 h and 71% versus 63% in defecation; and 13.77 h versus 14.21 h and 68% versus 67% in taking a shower.

Assessment of radioiodine clearance in patients with differentiated thyroid cancer

Radioiodine ((131)I iodide) has long been a safe, effective and widely used treatment in the management of differentiated thyroid cancer (DTC). Concerns regarding stochastic radiogenic risks have led to regulatory criteria for the release from medical confinement of patients who receive such radionuclide therapy. Over a 6-y period, the external whole-body dose rates at 1 m from 562 DTC patients were measured with an ionisation chamber calibrated in microsieverts per hour out to 5-d post-administration. Patients were stratified into four administered activity groups: 3.7 GBq (36.8 %), 5.55 GBq (47.3 %), 7.4 GBq (12.8 %) and 9.25 GBq (3 %). Consistent with previously published data, the current study demonstrated that a bi-phasic model accurately described (131)I-iodide kinetics up to at least 5-d post-administration in DTC patients, providing data that would be useful in formulating radiation safety guidelines for staff and other individuals coming into contact with such patients after treatment.

Thyroid cancer patients treated with 131I: radiation dose to relatives after discharge from the hospital

BACKGROUND

Thyroid cancer patients treated with radioiodine are potential source of radiation exposure for other individuals. Thus, we evaluated the radiation dose received by family members of thyroid cancer patients treated with (131)I after hospital discharge.

MATERIALS AND METHODS

Seventy-six family members of 56 thyroid cancer patients were included in the study. Thyroid cancer patients were given 3.7 GBq of (131)I and remained in a radiation protection ward for 3 days. Radiation protection recommendations were given to patients and relatives. Life conditions were recorded and radiation doses were monitored using a personal dosimeter.

RESULTS AND DISCUSSION

At discharge, the mean residual activity was 188 MBq. The mean radiation dose delivered to relatives during the 7 days after discharge was low (51.5 μSv) and was similar with either recombinant human thyrotropin (rhTSH) (59 μSv) or withdrawal (50 μSv) (p = 0.37).

CONCLUSION

With our current practice, radiation doses to relatives are low and well below international recommendations.

Estimation of the Release Time from Isolation for Patients with Differentiated Thyroid Cancer Treated with High-dose I-131

PURPOSE

Patients receiving high-dose I-131 to treat differentiated thyroid cancer are isolated from visitors to limit radiation exposure to reasonable levels. The appropriate isolation time is unclear and has not been reported in Korea. The purpose of this study was to estimate the isolation time and investigate the possibility of earlier release from isolation.

METHODS

This study was a retrospective analysis of data from 71 patients (10 men and 61 women; mean age, 49 ± 11.1 y) who received 3.7 GBq (47 patients), 5.55 GBq (23 patients), or 7.4 GBq (1 patient) of I-131 between January 2008 and December 2008. The radiation dose was measured with a fixed probe placed inside the isolation room. The total estimated dose equivalent (TEDE) to family members, the time required for the external dose rate to become <0.07 mSv/h, and the time required for whole-body retention to become <1.2 GBq were calculated.

RESULTS

By the TEDE criterion (<5 mSv), 70 of 71 patients (98.6%) could have been released without isolation. By the external dose rate criterion, 10 of 71 (14.1%) and 60 of 71 patients (84.5%) could have been released without isolation and within 24 h, respectively. With whole-body retention criterion, 19 of 71 (26.8%) and 48 of 71 patients (67.6%) could have been released within 24 h and within 48 h, respectively.

CONCLUSIONS

Appropriate release times were estimated and compared using different criteria. Most patients could have been released without isolation or within 24 h of radiation treatment.

Biodistribution and dosimetry of (131)I in thyroidectomy patients using semiquantitative gamma-camera imaging

The aim of this study was to determine the biodistribution, effective retention half-time (T(eff)), and internal organ dosimetry of (131)I administered to patients with papillary thyroid cancer after a total or near total thyroidectomy, and whole-body and organ activity was measured by gamma-camera imaging at 16 time points over 5 days following the administration of 1.1 GBq of (131)I in 5 patients. Whole-body scanning was performed by using a Siemens E-CAM() gamma-camera at a fixed distance of 5 cm from the patient. (131)I activity in regions of interest (ROIs) corresponding to the bladder, heart wall, kidneys, liver, lower gastrointestinal tract, lung, stomach, and thyroid remnants were measured, with measurements in the thigh used as the background. Most activity was localized to the lower gastrointestinal tract and thyroid remnants on day 1. The longest T(eff) was in the lung and the shortest was in the bladder (34.0 and 16.8 hours, respectively). The three organs with the highest absorbed doses per unit of administered activity were the lower gastrointestinal tract (2.03 mSv/MBq), the stomach (1.32 mSv/MBq), and the heart wall (1.24 mSv/MBq). T(eff) for thyroid remnants and the whole body were also estimated. We evaluated these organ doses to determine the normal tissues most likely at risk for stochastic and deterministic effects associated with (131)I therapy for thyroid cancer and benign disease. Our results represent preliminary findings, and the study will continue to accrue a greater number of study participants.

Hemodialysis of chronic kidney failure patients requiring ablative radioiodine therapy

Ablative radioiodine therapy is the standard treatment for thyroid carcinoma, but as (131)I is predominantly cleared by renal excretion, its clearance will be reduced in patients with chronic kidney disease, particularly in anuric patients on dialysis. The high dose of radioactivity used in the procedure results in an increased risk of radioactive exposure to the patient, the dialysis staff, and the machinery. Here, we describe how to successfully hemodialyze patients with chronic kidney failure requiring ablative (131)I therapy for thyroid cancer while minimizing risks to the patient and dialysis staff. With appropriate training, hemodialysis treatments can be safely delivered to patients receiving radiotherapy.