The effects of dialysis on 131I kinetics and dosimetry in thyroid cancer patients--a pharmacokinetic model

Radiation Protection Considerations for Cancer Patients with End-stage Renal Disease Receiving 131 I Treatment

ABSTRACT

Differentiated thyroid cancer (DTC) is commonly treated first with a partial or complete thyroidectomy, followed by radioiodine (RAI) ablative therapy to eliminate remaining cancer cells. In such treatments, physical decay and urinary excretion are the primary means of 131 I. As such, patients with impaired urinary ability clearance, such as patients with end-stage renal disease (ESRD) whose urinary ability is impaired by dysfunction, can retain abnormally high activities of RAI, posing a concern to both the patient and those with whom the patient interacts. Additionally, ESRD patients are commonly administered dialysis therapy, wherein their blood is externally cycled through a dialyzer (hemodialysis) or filtered by instilling a dialysate fluid into the peritoneum (peritoneal dialysis) to filter uremic toxins from their blood that accumulate due to kidney dysfunction. These factors make determining release and dosing for ESRD patients receiving RAI therapy dependent on a plurality of variables. An evaluation of the current patient release guidelines, as given in US Nuclear Regulatory Commission (US NRC) Regulatory Guide 8.39 Rev. 1 for ESRD patients receiving RAI, has yet to be addressed. In this study, a biokinetic model for 131 I in ESRD patients receiving dialysis has been developed, improving on traditional two-compartment models, reflective of kinetics from multi-compartment models with updated transfer coefficients modified to reflect the different physiological functions of compartments. This updated biokinetic model was integrated with Monte Carlo radiation transport calculations using stylized computational hermaphroditic phantoms to calculate dose rate coefficients in exposure scenarios and compared with those of the point source models of NRC Reg Guide 8.39 Rev. 1 (and the proposed verbiage in Rev. 2). Results demonstrated that the baseline models of Rev. 1 and Rev. 2 overestimated the effective dose rate to an exposed individual for the majority of time post-administration, where both models overestimated the total dose to the maximally exposed individual. However, the application of several patient-specific modifying factors to the Rev. 2 model resulted in an overestimation by only a factor of 1.25, and in general, the results produced with the patient-specific modifications provide improved convergence with the dose rate coefficients computed in this study for ESRD patients.

Safe use of radiopharmaceuticals in patients with chronic kidney disease: a systematic review

BACKGROUND

Patients with chronic kidney disease (CKD) may need to have their radiopharmaceutical dosage adjusted to prevent adverse effects and poor outcomes, but there are few recommendations on radiopharmaceutical dosing for this group of patients. The aim of this study is to provide an overview of the available information on radiopharmaceutical dose recommendations for patients with CKD.

METHODS

We performed a systematic literature review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. We conducted a literature search in the MEDLINE (PubMed) and Embase databases and screened potentially relevant studies using inclusion and exclusion criteria. We independently assessed the included observational studies' methodologies and extracted relevant data.

RESULTS

Of the 5795 studies first identified, 34 were included in this systematic review. These studies described three radiopharmaceuticals: [131I]sodium iodine, [18F]fludeoxyglucose, and [131I]iobenguane. Twenty-nine studies (85.3%) reported data on patients with CKD stage 5, while only three studies mentioned CKD patients in other stages (8.8%).

CONCLUSION

We found no consistent recommendations for radiopharmaceutical dosing in patients with CKD. Although some studies do mention dosing difficulties in patients with CKD, information is available for only a few radiopharmaceuticals, and recommendations are sometimes contradictory. Further research on radiopharmaceutical dosing in patients with CKD is needed to determine whether these patients require specific dosing, especially for therapeutic radiopharmaceuticals where a non-optimised dose may lead to an increased risk of toxicity for non-targeted organs. Including patients with CKD in studies and providing specific information about dosing in these patients should be a priority for the radiopharmaceutical community.

(131)I treatment in Differentiated Thyroid Cancer and End-Stage Renal Disease

PURPOSE

Radioiodine (RAI) is a cornerstone in the treatment of Differentiated Thyroid Cancer (DTC). In patients on haemodialysis due to End-Stage Renal Disease (ESRD), it must be used cautiously, considering the renal clearance of this radionuclide. Also, the safety of the procedure and subsequent long-term outcome is still not well defined. In 2001, we described a dosimetric method and short-term results in three patients, with a good safety profile. We hypothesize that our method is safe in a long-term scenario without compromising the prognosis of both renal and thyroid disease.

MATERIAL AND METHODS

Descriptive-retrospective study. A systematic search was carried out using our clinical database from 2000 to 2014.

INCLUSION CRITERIA

DTC and radioiodine treatment while on haemodialysis.

EXCLUSION CRITERIA

peritoneal dialysis.

RESULTS

Final sample n=9 patients (n=5 males), age 48 years (median age 51 years males, 67 years female group); n=8 papillary thyroid cancer, n=1 follicular thyroid cancer; n=5 lymph node invasion; n=1 metastatic disease. Median RAI dose administered on haemodialysis 100mCi. 7.5 years after radioiodine treatment on haemodialysis, n=7 deemed free of thyroid disease, n=1 persistent non-localised disease. No complications related to the procedure or other target organs were registered. After 3.25 years, n=4 patients underwent successful renal transplantation; n=4 patients did not meet transplantation criteria due to other conditions unrelated to the thyroid disease or its treatment. One patient died due to ischemic cardiomyopathy (free of thyroid disease).

CONCLUSIONS

Radioiodine treatment during haemodialysis is a long-term, safe procedure without worsening prognosis of either renal or thyroid disease.

[Management of iodine-131 ablation therapy for thyroid carcinoma in a patient on chronic hemodialysis]

Iodine-131 ablation therapy for thyroid cancer in the patient on chronic hemodialysis represents a real problem since the main route of elimination of radioiodine is urinary. There is no recommendation on the management of this treatment in the patient on hemodialysis. We report our experience of management of this treatment in a patient aged 38 years, undergoing hemodialysis for chronic renal failure, and who have been indicated the treatment with iodine-131 for papillary thyroid carcinoma high risk. After multidisciplinary discussions (nephrologists and specialists in nuclear medicine and radiation safety), it has been decided to treat the patient with continuous ambulatory peritoneal dialysis therapy (CAPD). Because of the low but continuous elimination of iodine in the case of CAPD, the patient received a reduced ablative (131)I dose of 1850 MBq, which is 30% of the usual dose delivered in subjects with normal renal function. The patient was hospitalized for four days in nuclear medicine unit and the (131)I radioactivity emitted from him was 2.5 μSv/h at one meter at his hospital discharge. In conclusion, CAPD in relay of hemodialysis is a technique of renal replacement therapy that can be suggested to minimize exposure to radioactivity to the patient, his family and the medical staff.

Relationship between estimated glomerular filtration rate and biological half-life of 131I. Retrospective analysis in patients with differentiated thyroid carcinoma

AIM

This retrospective study sought to investigate the relationship between biological half-life (t1/2 biol) of 131I and estimated glomerular filtration rate (eGFR) in patients with thyroid carcinoma.

PATIENTS, METHODS

96 patients with differentiated thyroid carcinoma (69 women, 27 men, mean age 64.0 ± 13.6 years) and diagnostic and therapeutic administration of 131I were considered. Patients with pronounced specific iodine storage were not included in the study. The eGFR was estimated according to the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula, the t1/2 biol via dosimetry. Patients were subdivided in groups with normal clearance (NC) (n = 37, 38.5%), medium clearance (MC) (n = 48, 50.0%), and low clearance (LC) (n = 11, 11.5%) (eGFR ≥ 90; 60-89; 15-59 ml/min per 1.73 m2, respectively). The relationship between eGFR and t1/2 biol of 131I was modeled using a power function.

RESULTS

The groups significantly differed in terms of age (NC 53.8, MC 68.6, and 78.0 years, respectively), serum creatinine levels (NC: 0.71; MC: 0.85; LC: 1.18 mg/dl), and t1/2 biol (NC: 0.53; MC: 0.71; LC: 1.01 days). The t1/2 biol was significantly influenced only by eGFR, and not by age, gender, or body weight. The relationship between t1/2 biol of 131I and eGFR was described by the formula t1/2 biol = 20.3 · eGFR-0.782.

CONCLUSIONS

The calculated relationship between renal function and t1/2 biol of 131I can be used in principle to estimate a dose reduction for patients with renal insufficiency. The model, however, gives erroneous results in individual cases and therefore a routine utilization cannot be recommended. Prospective studies are necessary, based on larger patient numbers and more accurate methods for dose rate measurement and GFR.

Correlation between external exposure and activity in patients undergoing 131I thyroid cancer therapy

The uptake and clearance of 131I activity for inpatients undergoing cancer therapy were determined from routine external dose survey measurements. A bi-exponential behavior was found, with the two time constants representing the iodine dynamics in the thyroid on one hand and in the rest of the body on the other. The external dose at 1 m from the patient was correlated to the activity in the thyroid remnant and inside the body, the averaged value being 52.8 +/- 11.4 microSv GBq(-1) h(-1). The temporal evolution of activity in the body, the urinary system and the thyroid remnant area were determined taking into account the clearance from thyroid and whole body (effective retention constants averages 0.23 +/- 0.14 d(-1) and 1.46 +/- 0.34 d(-1)) and the uptake in thyroid (3.15 +/- 3.36%). Applications of this study in the public and environmental radiation protection areas are presented.

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.

[Hemodialysis procedure in a patient treated with radioactive iodine]

The treatment of a patient with 131I at activity over 740 mega Becquerel (MBq) must be performed in a nuclear medicine department. Isolation is stopped if the patient radiation level is less than 20 muSv/hour at one meter. As regards patients with chronic renal failure treated with hemodialysis (HD), the first HD session will eliminate the major part of the radioactivity. French regulations do not give definite recommendations for this session. However, it imposes to collect liquid and solid wastes contaminated by radioactivity. Thus, it seems necessary to collect dialysate and solid wastes and to stock them in a room dedicated to radiation decay. The risk for dialysis staff is to be contaminated by an accidental ingestion of a biologic fluid from the patient. The usual protection barriers used during the HD session are sufficient: mask, gloves, overgarments, cap. There is no risk linked to external exposure to radiations. The maximal theoretical dose received by the staff during the session is 65 muSv, while annual maximal dose for public exposed to radiations is 1000 muSv. Although the dosimetric follow-up of dialysis staff is not mandatory, the nuclear medicine department of Marseille University Hospital has decided to do it in an information perspective. The session is performed in the presence of a radiation safety technician who gives film badges and active dosimeters to the dialysis staff. He reports the dialysis staff to the nuclear safety agency (Autorité de sûreté nucléaire).