#2704 MANAGEMENT OF HAEMODIALYSIS PATIENTS UNDERGOING RADIOACTIVE IODINE THERAPY FOR THYROID CANCER

Abstract

Abstract Background and Aims Radioactive iodine (RAI) 131I is used in the adjuvant treatment of thyroid carcinoma following thyroidectomy. 131I is renally excreted, with reduced clearance in patients with end-stage kidney disease (ESKD). There are no established protocols for RAI dosing, timing of dialysis and safety in this population [1]. We describe a single-centre experience with a modified protocol and setup for RAI in haemodialysis (HD) patients including serum 131I measurements to monitor for red marrow toxicity. We present the outcomes in two HD patients. Method A protocol was developed for performing HD post-RAI administration. HD sessions were performed at 24, 72 and 144 hours post-treatment. Custom HD plumbing was installed within existing lead-lined infrastructure. Specific considerations were made for radiation safety including emergency protocols, handling of blood samples, nursing education, patient self-cannulation and dose-reduction of thyrogen pre-treatment. In addition to standard dose-rate meter measurements of radiation, serum 131I measurements were taken pre- and post-HD as a more accurate measurement of red marrow toxicity. Results The two patients included in the study were aged 41 and 60 years. Special considerations for these patients included anuric state in one patient (bilateral nephrectomy) and morbid obesity in the other. Both had early-stage papillary thyroid cancer treated with thyroidectomy. Retained radioactivity measured by dose-rate meter is shown in Figure 1. The largest reduction in radioactivity occurred after the first HD session (approximately 60%). The highest risk of radiation exposure was in the 24 hours prior to the first HD session. Pre-and post-HD serum 131I measurements estimated the radiation dose to red marrow to be below 0.2Gy (maximum tolerated radiation dose for red marrow is 2.0Gy2). Radiation received by HD nurses is shown in Figure 2. Overall exposure was well within national regulatory dose limit of 0.5mSv for members of the public. Conclusion HD at 24, 72 and 144 hours produced a radiation clearance profile similar to controls with normal renal function. The effect of residual renal function on 131I clearance was minimal and HD was the main determinant of 131I clearance in ESKD. Non-routine serum measurements of 131I can be used to assess toxicity to red marrow and guide HD session timing during RAI therapy. Performing HD at 24 and 72hrs post- 131I resulted in a radiation burden to the red marrow well below the accepted radiotoxicity threshold of 2Gy [2]. RAI can be given safely to HD patients with thyroid cancer in centres with the appropriate protocol and setup.