Guidance on patient preparation and radiation protection for patients undergoing radioiodine treatment for thyroid cancer

Patient Preparation Prior to Treatment

Low Iodine Diet

• Consider a LID for 1 week (or 2 weeks maximum) depending on local preference.
• Withhold iodine-containing vitamin supplementation for 1–2 weeks prior to ¹³¹I.
• A simple and concise LID information leaflet is strongly advised.
• Normal diet to be resumed on the administration of ¹³¹I.
• Routine urinary iodine concentration (UIC) measurement to ensure LID compliance is not recommended outside a clinical trial.

Recombinant thyroid-stimulating hormone versus thyroid hormone withdrawal

• The Standard rhTSH regimen is 0.9 mg intramuscular injection 48 and 24 h prior to RAI, following total thyroidectomy.
• rhTSH preparation prior to RAI ablation is strongly recommended if all of the criteria are met: T1-T3, N0/N1/Nx, R0, DTC.
• rhTSH preparation prior to RAI ablation may be considered if any or all of the criteria are met: T4, R1/2, and DTC (but caution advised if bulky macroscopic residual disease). It should be noted that this is an unlicensed indication.
• rhTSH preparation prior to RAI therapy for locoregional recurrence and/or M1 DTC may be considered (but caution advised if adjacent structures will be compromised by tumor flare). It should be noted that this is an unlicensed indication.
• Thyroid hormone withdrawal (THW) is absolutely contraindicated in hypopituitarism and relatively contraindicated if there is exogenous tumor production of T3/T4.

Medical indications for delay prior to radioiodine

• Pregnancy is an absolute contraindication to RAI and must be excluded by human chorionic gonadotropin (hCG) test within 48 h of RAI administration.
• Breastfeeding and lactating must be discontinued at least 8 weeks prior to RAI and not resumed until after a subsequent pregnancy.
• Following administration of iodinated radiology contrast media, a minimum interval of 8 weeks is recommended prior to RAI ablation or therapy, but this can be reduced to 4 weeks if clinical circumstances dictate earlier treatment (providing estimated glomerular filtration rate [eGFR] is normal).
• If diagnostic whole-body scintigraphy (DxWBS) is performed prior to RAI ablation or therapy, ¹²³I (or ¹²⁴I) is preferable, but ¹³¹I can be utilized provided activity is <400 MBq to minimize risk of stunning. This is not routinely recommended and should be considered investigational.
• Consider withholding amiodarone for 12 months prior to RAI ablation or therapy, if clinically appropriate.

Continence/contamination risk assessment

• Urinary catheter advised for moderate to severe urinary incontinence, especially in the first 24 h following RAI administration.
• Individual guidance for patients (and/or carers) is required on handling and disposing of incontinence pads or bladder/bowel stoma pouches following discussion with the Radiation Protection Advisor (RPA).
• Capsule form of ¹³¹I is the preferred form of administration.
• For patients with swallowing difficulty, speech and language therapy assessment and coaching with dummy capsules should be considered. With appropriate support, most patients will manage to swallow a capsule.
• In the exceptional circumstances that administration by capsule is not possible, oral liquid or intravenous administration can be considered subject to appropriate risk assessment.
• Scheduling of non-urgent medical interventions should be delayed where possible.
• Unavoidable interventions (for example, daily injections) should be self-administered if feasible.
• Individual guidance for patients (and/or staff) pertaining to handling and disposing of medical equipment is required following discussion with the RPA.
• Visits to an RAI unit should be minimized. It is inappropriate for people who are pregnant and have children to visit relatives or friends undergoing RAI treatment.
• Visits should be limited to 60 min maximum, no sooner than 24 h after administration, at least 1 m distance, and the controlled area should be clearly demarcated.
• Consider a 50% dose reduction in rhTSH (0.9 mg 48 h prior to RAI or 0.45 mg 48 h and 24 h prior to RAI).
• Consider a 25–50% reduction in the prescribed activity of ¹³¹I depending on individual clinical and pathological risk factors.
• Haemodialysis should be carried out as a minimum of 48 h before and 24 h after RAI.
• A dedicated hemodialysis unit is required, preferably within the RAI unit.
• Individual guidance for staff pertaining to handling and disposing of medical equipment/dialysate is required following discussion with the RPA, including the use of personal dosimeters.
• Delay discharge from RAI unit until the retained activity is ≤30 MBq.

Individualized Discharge Advice 

Individualized discharge planning and methods of monitoring

• Serial measurements of external dose rate or residual activity should be used to guide the time of discharge and to aid individualized radiation protection advice.
• Patients can be considered for discharge when the residual activity falls below 800 MBq or the external dose rate falls below 40 μSv/h at 1 m.
• The decision to discharge a patient who retains more than these levels should be based on an individual risk assessment, taking into account the home circumstances, particularly the ability and willingness of all potentially exposed individuals to comply with the advice given to them to restrict their exposure.
• Contact restrictions should be based on serial measurements and individual risk assessment. For patients receiving ablative doses, only rarely are these likely to exceed 7 days post-administration. For patients receiving a therapeutic dose, in a minority of cases restrictions may extend for a longer period, but are unlikely to exceed 14 days.

Practical advice for patients

• Patients should take their personal clothing home and wash it separately from other items before use. Clothes can be washed at regular temperatures, there is no need for a hot wash. Clothes should not be stored by the hospital.
• Personal electronic items may be used uncovered (gel-type phone protectors should be discouraged) and decontaminated by the patient prior to discharge. These should be kept for the personal use of the patient during the period restrictions apply.
• Patients should avoid sharing a bed and having sexual intercourse during the period they are under restrictions.
• There is no need to limit contact with animals or pets.
• Patients should be encouraged to shower daily and drink plenty of water during the period they are under restrictions.

Day Case Ablation Therapy with 1.1GBq 131I