Iodine 131 therapy is an important adjuvant treatment for thyroid cancer after surgery. After years of clinical experience, we have concluded that there are five misconceptions about iodine 131 therapy among thyroid cancer patients.
Myth 1: Iodine 131 therapy is no longer needed because the surgery is clean
Iodine 131 treatment includes “nail clearing” (removal of thyroid tissue) and “treatment”. The term “nail clearing” refers to the use of iodine 131 to destroy the normal thyroid tissue that remains after surgery. The theory is that, unlike other cancers, most thyroid cancers occur in multiple centers, and even if there is only one cancerous nodule in the thyroid gland detected by CT, ultrasound or surgery, there may be cancer cells in other parts of the thyroid gland that have not formed obvious cancerous nodules because of the small number of cancer cells. Some people think that a good surgeon will remove all the thyroid gland and no normal thyroid tissue or cancerous tissue will be left. This is a misconception. Even a good surgical specialist can only remove the thyroid gland or cancerous tissues with the naked eye, but not completely under the microscope, i.e. there are still a small amount of thyroid cells or cancerous cells left after surgery, and these residual thyroid cells or cancerous cells must be destroyed by taking iodine 131.
Taking advantage of the ability of papillary thyroid cancer and follicular cancer cells to highly ingest and concentrate iodine, patients are allowed to take iodine 131 orally, which will be specifically absorbed by thyroid cancer cells when it enters the body, and the beta radiation released by iodine 131 will destroy thyroid cancer cells hidden in any part of the body. Many patients with thyroid cancer treated with Iodine 131 have the same life expectancy as normal people. Therefore, iodine 131 therapy for thyroid cancer patients after surgery will bring great benefits to patients, significantly prolonging their survival and reducing the recurrence of cancer.
Of course, not all thyroid cancer patients will benefit from treatment with 131 iodine. In general, radioactive iodine therapy is more effective for papillary and follicular carcinoma and can be used as an adjuvant therapy for post-surgical and concurrent soft tissue metastases. However, it is less effective in the treatment of skeletal metastases or large nodal metastases in the lungs. Before treatment, it is important to know whether it can concentrate iodine 131; if the cancer tissue cannot concentrate iodine 131, it is not suitable for iodine 131 treatment, regardless of the pathological type. It is worth noting that some of them cannot concentrate iodine 131 at the beginning, but after various pretreatments, the lesions can concentrate iodine 131 and can still be treated with iodine 131. As for undifferentiated carcinoma and medullary carcinoma, they generally do not respond to radioactive iodine therapy. Early stage low-risk differentiated thyroid cancer is very effective with iodine 131 treatment surgical treatment plus thyroxine suppression, and further iodine 131 treatment does not benefit. There is also no consensus on whether radioiodine therapy should be given repeatedly to patients who also have distant metastases but are clinically asymptomatic. In particular, clinicians must consider whether the high TSH concentration in the blood that must be adjusted before each administration of radioiodine therapy may accelerate the growth of cancer cells. Currently, iodine 131 therapy is not required for differentiated thyroid cancer with a diameter of less than 2 cm and without lymph nodes or distant metastases. For those with cancer foci larger than 2 cm in diameter, or those with microscopic extra-thyroidal infiltration or lymph node metastasis, iodine 131 therapy can be recommended. For cancer foci with diameter greater than 4 cm, or cancer foci with microscopic extra-thyroid infiltration, or distant metastasis, iodine 131 treatment must be done.
Myth 2: Some thyroid cancer patients do not need to consider iodine 131 treatment because they have not taken iodine 131 and have not recurred.
Thyroid cancer is a kind of tumor that grows more slowly than other malignant tumors. Within 3-5 years, it is difficult to determine whether the cancer has recurred by ultrasound or CT alone without ECT examination or blood sampling for thyroglobulin assay, but the patient may already have smaller cancer lesions in his body. Studies have shown that the recurrence rate of patients treated with iodine 131 after thyroid cancer surgery is one-third of those who did not have iodine 131 treatment. In clinical practice, we often find that patients with thyroid cancer who have not taken iodine 131 are cured 3-5 years after surgery by ECT scan after taking small doses of iodine 131 orally, and metastases or recurrence foci are found in the lymph nodes or thyroid bed area of the patient’s neck. treatment.
Misconception 3: Iodine 131 has great side effects
The side effects of radioactive iodine are not significant. The therapeutic dose of iodine 131 forms direct radiation damage to thyroid cancer lesions, residual thyroid tissue, adjacent tissues and other normal tissues and organs that can take in iodine, which can lead to different degrees of radioactive inflammatory reactions. Common side effects in the short term (1-15 days) after nail scavenger treatment include weakness, neck swelling and throat discomfort, dry mouth and even swollen salivary glands, altered taste, nasolacrimal duct obstruction, upper abdominal discomfort and even nausea, and urinary tract damage. Most of the above symptoms appear within 1-5 days of nail clearing treatment and often resolve on their own without special treatment. Some studies have shown that taking acidic candy, chewing sugar-free gum, massaging salivary glands or rehydration can reduce the radiation damage to salivary glands during iodine 131 treatment. Measures such as drinking plenty of water, urinating more often and taking laxatives may help to reduce radiation damage to the abdominal and pelvic cavities, but attention should be paid to the possibility of electrolyte disturbances. In patients with other chronic diseases and/or advanced thyroid cancer, persistent hypothyroidism combined with damage from iodine 131 after nail cleansing, the underlying disease may worsen in the short term and needs to be closely observed and promptly treated. In addition, patients may experience some psychological changes such as boredom, anxiety, insomnia, fear, etc. in the short term after nail clearing treatment, which are not a direct result of iodine 131 damage, but originate from some factors during the treatment implementation (such as radiation protection isolation, gradual aggravation of hypothyroidism and other disease effects, etc.).
In the early days of iodine 131 treatment, serious side effects such as leukemia, suppressed reproductive function, second primary carcinoma, pulmonary fibrosis, degenerative developmental changes, etc. were reported due to the lack of attention to the maximum safe dose experience. Nowadays, the reports of serious side effects after iodine 131 treatment have been greatly reduced due to the emphasis on the maximum safe dose experience. International studies have confirmed that taking a safe dose of iodine 131 does not have long-term effects on fertility (but note: iodine 131 treatment is not recommended during pregnancy, lactation, or planned pregnancy within 6 months), does not lead to an increased incidence of cancer such as leukemia in patients, and has significantly lower side effects than chemotherapy and radiotherapy. One dose of iodine 131 is less than the radiation received by the patient from one chest X-ray. The process of taking Iodine 131 is simple. Patients only need to pick up a small glass bottle containing 2 ml of colorless and tasteless liquid, drink it and rinse their mouth with water to complete the treatment.
Misconception 4: ECT test is done after surgery before deciding whether to take Iodine 131
For patients who need to take iodine 131 treatment, it is not necessary to do ECT examination first. This will affect the efficacy of taking high dose of iodine 131 for thyroid cancer treatment, which is known as “suppression” in academic circles.
Myth 5: Patients with thyroid cancer do not need to go to hospital for review after surgery if they take iodine 131
Iodine 131 can greatly reduce the probability of recurrence and metastasis, but there are still a few patients who have recurrence and metastasis. Therefore, patients who are cured by ECT scan after taking iodine 131 should be reviewed in 1 year, and if there is no problem in the review, review in 2 years, and if there is no problem, review every 5 years. Items for review: thyroid ultrasound, ECT whole body scan, blood thyroglobulin level, thyroid function, etc.
Appendix 1 Precautions for iodine 131 treatment
1. Before iodine 131 treatment, stop taking eugenol or thyroid tablets for about 2 weeks, in order to raise TSH in the body and promote the uptake of iodine 131 by the lesion.
2. A low iodine diet (avoiding seafood and iodine-rich foods and drugs) must be taken for 2-4 weeks before iodine 131 treatment, also to increase the uptake of iodine 131 by the lesion.
3. Due to the large amount of radioactivity in the patient’s body after oral iodine 131 treatment, hospitalization is required for high-dose iodine 131 treatment. Family members are not allowed to accompany the patient during the isolation period.
4. If you have other systemic diseases, please consult with the appropriate specialist before hospitalization, and only after the other diseases are stabilized, iodine 131 treatment can be administered.
Appendix 2 Steps of iodine 131 treatment for thyroid cancer
The first step is to surgically remove the primary foci and metastases, the second step is to eliminate the residual normal thyroid gland with iodine 131, and the third step is to perform whole body imaging and treatment with iodine 131. If only the remaining thyroid gland is found to ingest iodine 131, after complete removal of the residual normal thyroid tissue, regular follow-up is performed; if the patient is found to have metastatic foci, treatment can be started and can be repeated every 3-4 months under normal circumstances.
After complete removal of residual normal thyroid tissues, the recurrence rate of thyroid cancer is significantly reduced; the 5-year survival rate is significantly increased; regular review for recurrence program is to draw blood and test TG (thyroglobulin) to determine, the test is low cost, convenient and can detect whether there is recurrence at an early stage.