Radiation doses to cohabitants of patients undergoing radioiodine ablation for thyroid cancer: poor compliance with radiation protection guidelines but low radiation exposure.

Background: The drive to reduce hospital stay after radioiodine remnant ablation in patients with thyroid cancer may increase the risk of radiation exposure to family members. The aim of this study was to evaluate the key determinants of dose exposure to familial members, with particular reference to the degree of adherence to current radiation safety guidelines.

Methods: All participants prospectively received our standard departmental oral and written safety instructions, with a mandatory 3-day restriction period. The postmicturition radiation levels of treated patients were measured (at 1-m distance) at the time of discharge using a portable radiometer. The radiation exposure of cohabitants was assessed with an optically stimulated luminescence-based personal dosimeter during the 3 days after hospital discharge. A questionnaire was used to assess the adherence of relatives/cohabitants to radiation safety guidelines.

Results: A total of 38 patients with thyroid cancer and 48 household members were included. At 48 h post therapy, the patient's median emission at 1-m distance was 13.4 μSv/h. The mean cumulative cohabitant exposure was 102 μSv (<50-1000). A positive correlation between cohabitant radiation exposure and the radiation level of the patient was observed (P=0.016). This correlation was absent when the recommended guidelines were followed (P=0.56). Only 17 household members (35.4%) strictly followed the recommended guidelines, but dose exposures exceeded 0.3 mSv in only four cases, in which a mean of between 5.8 and 9.5 h were spent in close proximity to the patient in the first 3 days, including sleeping with treated patients in half of the cases.

Conclusion: Despite poor compliance with safety guidelines, a short-stay protocol respects current legislation, and is applicable to most patients treated with 3.7 GBq for radioiodine remnant ablation.