Iodine 131 (I-131) is a radioactive substance. So, is it safe to receive radioactive iodine (RAI) treatment after thyroid cancer surgery?
In fact, compared to radiation and chemotherapy, RAI treatment has far fewer side effects and does not cause severe vomiting, hair loss, or hematuria. The treatment usually has only mild gastrointestinal reactions and swelling of the neck and parotid glands, most of which will resolve on their own, and some patients with severe reactions can be relieved with targeted treatment, with essentially no impact on daily life and work.
Here are some specifics.
Adverse effects of RAI
Early reactions
These are the adverse reactions that can occur during treatment. Most of these symptoms improve on their own.
- Gastrointestinal upset (nausea and vomiting)
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Approximately 30% of adult patients experience symptoms, with more pronounced symptoms in children. gastrointestinal distress caused by RAI often occurs about 4 to 12 hours after dosing and usually subsides after 36 hours.
- Salivary gland inflammation/dry mouth
Salivary glanditis is inflammation and enlargement of the parotid and sublingual glands, which may present as fever, pain, dry mouth, difficulty swallowing, and facial swelling. The incidence is about 30% in adults. Metastases from thyroid cancer treated with high doses of iodine are more likely to develop salpingitis and laryngeal edema, usually within a week of treatment.
To relieve inflammation, take prednisone tablets by mouth in moderation under medical supervision. Oral vitamin C tablets or regular chewing of gum may encourage saliva production and prevent or reduce damage to the salivary glands from radiation.
To relieve discomfort such as dry mouth, acidic candy or vitamin C can usually be started within one day of taking I-131 orally for 3 days. After taking I-131, you should drink plenty of water and take a laxative (such as aminoglutethimide) to promote excretion and reduce side effects. However, drinking large amounts of water for excretion may trigger electrolyte disturbance and symptoms such as fatigue, cramps and spasms.
- Bone marrow suppression
Bone marrow suppression is overwhelmingly temporary, occurring in about 25% of cases, with permanent bone marrow suppression rarely occurring. It typically results in a decrease in white blood cell and platelet counts for 6 to 10 weeks and drops to a minimum 1 to 2 months after treatment, and usually resolves on its own within 6 to 12 months.
The severity of myelosuppression depends largely on the number of bone metastases and the amount of I-131 taken up by the lesions.
- Dry eye disease
A very small number of patients will also experience temporary dry eye and lacrimal gland dysfunction after RAI treatment, and the majority will resolve on their own.
Long-term reactions
These complications will persist for a long time or occur some time after the end of treatment.
- Radiation pulmonary fibrosis
Patients with differentiated thyroid cancer with diffuse lung metastases who receive repeated higher doses of RAI over a short period of time may develop pulmonary fibrosis. You may have symptoms such as cough, shortness of breath, and fever that worsen with treatment.
If the cough and shortness of breath are only mild on CT, but there are no symptoms, or only a mild dry cough, no medication is needed; if the cough and shortness of breath are mild and there is no fever, only oral cough syrup or phlegm and wheezing medications are needed, and antibiotics can be considered to prevent infection; if the cough and shortness of breath are severe and interfere with daily life, or if they are accompanied by high fever and CT shows If the cough and shortness of breath are severe, affecting daily life, or accompanied by high fever and CT showing obvious exudation, RAI treatment needs to be stopped immediately, and glucocorticoids, oxygen and, if necessary, ventilators need to be added along with intravenous anti-inflammatory therapy.
It is important to note that once hormones are administered, they must be administered in full doses and courses, with gradual tapering after symptoms are controlled and imaging is significantly better. The dose should be increased or decreased as prescribed by your doctor, and you should not increase or decrease or stop the medication on your own to avoid rebound.
- Second primary malignant neoplasms (SMN)
The incidence of SMN may be increased with long-term, high-dose application of I-131 (usually at doses cumulatively greater than 500 to 600 millicuries), but the overall risk is low. Possible SMNs are leukemia, bladder malignancy, and colorectal cancer.
It is important to note that if you have a combination of other chronic conditions, or if you are an advanced patient with persistent hypothyroidism, plus damage from clearing the nail, the underlying disease may worsen in the short term and you need to keep a close eye on your condition and call your doctor for any abnormalities.
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Co-written by Dr. Xiaoke Zheng, Fudan University Cancer Hospital