Outpatient treatment of thyroid cancer using high doses of iodine 131.

OBJECTIVE: To develop a protocol for outpatient high-dose iodine 131 therapy to treat thyroid cancer, to allow therapy to be performed at the patient's convenience and save considerable hospital costs without causing undue radiation exposure to members of the public.

METHODS: The radiation safety hazard--both external (from gamma rays emitted from the patient) and internal (from radioactive material in the patient's excretions)--can be calculated according to guides issued by the US Nuclear Regulatory Commission. The protocol aimed to produce an "occupancy factor" of 0.125 or less for the "critical person" (person caring most for the patient) for the entire 72-hour period after administration of 131I. This is the equivalent of 3 hours per day at a distance of 1 m from the patient.

RESULTS: Each patient's suitability for outpatient therapy is determined on the basis of the patient's home environment, ability to understand the risks involved and likelihood of compliance, by the referring physician's opinion, through a self-report questionnaire and through a patient interview with the radiation safety officer and the nuclear medicine physician. This protocol has been approved by the Atomic Energy Control Board and has been used to screen 8 patients to date, with 1 patient being denied outpatient treatment.

CONCLUSIONS: Outpatient therapies with relatively high doses of 131I can be performed safely. Care must be taken to ensure that the patient's home environment is suitable and that the patient can understand and comply with precautions. If external exposure can be minimized, only basic precautions are needed to ensure that internal contamination does not lead to excessive doses to members of the public.