Radioactive iodine (I-131) (RAI) therapy is one of the mainstays of postoperative treatment for differentiated thyroid cancer. You may be concerned: Am I a “walking radiation source” after this treatment? What do I and my family need to be aware of?
How long does it take to get rid of radioactive iodine?
Iodine-131 (Iodine-131)
Iodine-131 (I-131) is a radioisotope with a physical half-life of 8.04 days, which means that after 8 days the radioactivity is reduced by half on its own. With the body’s biological excretion, the radioactivity in the body is very low after 8 days.
The literature reports that approximately 90% to 95% of the radioactive iodine is excreted within 1 week of taking the drug, and not much remains in the body at the time of discharge. Clinical tests have also confirmed that after iodine administration, as long as a whole-body scan reveals no iodine-enriched primary or metastatic lesions, more than 95% of the radioactivity in the body has been eliminated after 5 days, with only about 1% to 5% remaining.
After treatment, do I need to be “quarantined”?
Do I need to be “quarantined” after treatment?
After taking I-131, you are indeed a “walking radioactive source” for a short period of time, especially with the radioactive iodine in your excretions, which can contaminate the environment and therefore must be properly isolated. The general requirement is 2 weeks after treatment, after which there is no effect on others.
According to international and national industry standards, for the average person, the annual dose of radioactive radiation should be less than 1 mSv (mSv is a unit of equivalent radiation dose measured as absorbed by the body). One study showed that patients with differentiated thyroid cancer were discharged on day 3 after taking I-131, and if the average radiation dose on day 3 was based on 10 hours of exposure to the patient per day (calculated at a distance of 1 meter or 3 meters) by the caregivers, the cumulative radiation dose for half a month was less than 1 millisievert. Therefore, it is safe for caregivers to maintain a distance of 1 meter or more on day 3 after treatment with iodine-131 in patients with differentiated thyroid cancer.
How can I reduce my family’s exposure to radiation?
Usually, the residual radioactivity in the body at the time of discharge is low, but because the total dose taken is large (usually greater than 100 millicuries. The milli-curie is a unit of measurement of the “activity” of the radioactive source), it is important to avoid close contact with family members after discharge. If you have a pregnant woman or infant in your home, you need to pay extra attention.
Try to do the following:
- Doctors usually recommend that you drink plenty of water and urinate repeatedly for 3 days after taking iodine to get rid of the radioactive content that is trapped in your body as soon as possible and to reduce its radiation to your gonads.
- During hospitalization, the hospital’s nuclear medicine department has special equipment to handle excretion. After discharge, the excrement goes directly to the toilet, so it is important to flush the toilet with water after urinating and defecating for 1 week to prevent the radioactive excrement from remaining.
- It is best to wash underwear separately.
- Remain more than 1 meter away from your family for 1 week after discharge, and avoid close contact for more than 1 month if you have pregnant women or children under 10 years old.
- Go to work after 1 week of isolation and keep 1 meter or more between colleagues (based on 8 hours of contact per day).
Co-written by Dr. Xiaoke Zheng, Fudan University Cancer Hospital