# Management of radioiodine ablation therapy in haemodialysis patients with thyroid cancer: a case series of two patients

## TL;DR

This paper presents a safe approach for administering radioiodine therapy to patients with kidney failure undergoing dialysis, using modified protocols and safety measures.

## Contribution

The study provides a practical framework for safely delivering radioiodine therapy to hemodialysis patients with thyroid cancer.

## Key findings

- Hemodialysis at specific intervals post-treatment reduced radiation exposure to safe levels comparable to patients with normal kidney function.
- Bone marrow radiation doses remained below 0.3 Gy, indicating safety for both patients.
- Staff radiation exposure was well within safety limits, at 7μSv and 23μSv for the two patients.

## Abstract

Radioiodine (131I) therapy in treatment of thyroid cancer, has a biological clearance that is significantly reduced in end-stage kidney disease (ESKD), leading to increased radiation exposure and potential myelotoxicity. For ESKD patients on haemodialysis (HD), there is no standardized approach to 131I administration and subsequent HD schedule.

Two patients with ESKD on HD were treated with 131I therapy for thyroid cancer. Rationale for treatment and local 131I treatment protocol modifications are discussed. Modifications were made to existing infrastructure and additional patient and staff safety precautions were undertaken, including serum radioactivity measurements to monitor for myelotoxicity.

HD at 24-,72- and 144-hours post-131I results in a retained radiation activity profile comparable to patients with normal renal function. Radiation dose to bone marrow throughout treatment was assessed at < 0.3 Gy for both patients, within safe limits. The highest contribution of radiation dose to bone marrow (60% and 47% for patient 1 and patient 2 respectively) was due to the radioactivity retained in blood before the first HD session. Cumulative radiation exposure to dialysis staff was well within local safety constraints (300μSv per year) at 7μSv and 23μSv for patient 1 and 2 respectively. At 24 months post-therapy, thyroglobulin levels remained undetectable for both patients.

131I therapy can be safely administered in patients with ESKD on HD with low-risk thyroid cancer through modifications to existing infrastructure and protocols. Serum radioactivity measurements is a simple and minimally invasive method to assess bone marrow safety during treatment. Ongoing pooling of experiences is needed to inform a standardized protocol for therapy in this population.