131 iodine (131I) treatment for differentiated thyroid cancer Q&A
1.What kind of disease is thyroid cancer?
Thyroid cancer is the most common type of primary malignant tumor of the neck, accounting for about 1% of all malignant tumors. Pathologically, it is divided into four categories: papillary carcinoma, follicular carcinoma, undifferentiated carcinoma and medullary carcinoma. The real cause of thyroid cancer is still unclear, but it may be related to the following factors
(1) Thyroid cancer is more likely to occur in people who have received X-ray or radiation treatment on the head, neck or upper chest during childhood.
(2) Patients with Hashimoto’s thyroiditis with thyroid nodules are more likely to develop thyroid cancer.
(3) Family genetic factors.
(4) Abnormal iodine intake: Excessive iodine intake or iodine deficiency can change the structure and function of the thyroid gland, which may be related to the occurrence of thyroid cancer.
2.Is the incidence of thyroid cancer high?
Thyroid cancer accounts for 3.8% of malignant tumors in human body (1.7% in men and 5.8% in women). Male:female=1:3~4, it is the solid cancer with the fastest increasing incidence. Statistics from the United States found that the incidence of thyroid cancer increased 5-fold between 1989 and 2012. The growth of thyroid cancer incidence in China is equally serious, with a significant rising trend throughout the country, and thyroid cancer has taken the 1st place of female malignant tumor incidence in Hangzhou in 2013.
The rising trend of thyroid cancer incidence is manifested by the rise in various races, genders, ages, tumor sizes, and tumor stages. The rise in the incidence of thyroid cancer cannot be explained by the massive use of ultrasound alone. It shows that the real increase of thyroid cancer incidence is a fact that cannot be avoided!
3.What are the types of thyroid cancer?
There are 4 types of thyroid gland.
(1) Papillary carcinoma: the most common, derived from follicular epithelial cells, accounting for about 80% of thyroid cancer.
(2) Follicular carcinoma: the second most common type.
(3) Undifferentiated carcinoma: rare, extremely malignant.
(4) Medullary carcinoma: derived from parathyroid cells (a kind of neuroendocrine cells) and is more malignant.
Among them, papillary carcinoma and follicular carcinoma are the more differentiated thyroid carcinomas, which together are called differentiated thyroidcancer (DTC), accounting for more than 90% of all thyroid carcinomas.
4.What are the diagnostic tools of thyroid cancer?
(1) Neck ultrasound: High-resolution ultrasound is the preferred method to evaluate thyroid nodules. The ultrasound features of the thyroid nodule are used to determine whether it may be a thyroid cancer.
2) Thyroid scan: The functional status of thyroid nodules is observed using isotope imaging to determine the likelihood of benign and malignant nodules.
(3) CT: CT is of clinical significance in determining the benignity and malignancy of thyroid tumors and distinguishing solid from cystic.
(4) Fine needle aspiration cytology: biopsy of thyroid nodules or cervical lymph nodes using fine needle aspiration can often confirm the diagnosis. It is an important means to confirm the diagnosis.
5.What are the treatment methods of DTC? How to treat thyroid cancer most effectively?
The treatment of most well-differentiated DTC requires 3 steps: 1) thyroidectomy, the main procedures are total thyroidectomy or subtotal thyroidectomy. Cervical lymph node dissection is a routine component of radical thyroid cancer treatment; 2) postoperative TSH suppression therapy, which reduces the risk of recurrence of DTC by suppressing TSH with more than physiological doses of eugenol (levothyroxine); 3) postoperative 131I therapy, which significantly reduces the chance of recurrence and metastasis in DTC after 131I therapy compared to patients treated with surgery and TSH suppression therapy only. significantly lower.
The combination of “surgery + TSH suppression + 131 iodine therapy” is the most ideal and effective treatment plan for DTC internationally.
6.How to determine whether the risk of thyroid cancer recurrence after surgery is high or low?
7.Why should thyroid cancer be treated with radioactive 131 iodine “nail cleansing” therapy? What is the purpose of treatment?
”The purpose of “nail clearing” is to remove the residual thyroid tissue after surgery.
Prevent or reduce the recurrence and metastasis of DTC
To prevent or reduce the recurrence and metastasis of DTC by detecting thyroglobulin (Tg) and 131I systemic imaging after treatment
To remove residual thyroid tissue with high iodine uptake capacity as the basis for focal clearance treatment (to increase the 131I uptake rate of metastases)
131I whole-body imaging after thyroid clearance helps to determine the severity of DTC more accurately and to formulate appropriate patient follow-up and treatment plans
Treatment of possible potential DTC lesions and killing of residual cancer cells
8.Which thyroid cancer patients should be treated with radioactive 131 Iodine after surgery? (Indications)
That is: DTC with cancer foci >1cm and/or extra-glandular infiltration or metastasis (lymph node metastasis and/or distant metastasis) can be considered for 131I nail clearing treatment after surgery
9.How does radioactive 131 iodine play a therapeutic role in DTC treatment?
DTC and its metastases have the ability to collect 131 iodine. After giving high dose of 131I, the cancer tissue is effectively suppressed and destroyed by the ionizing radiation of sufficient amount of beta rays to achieve the therapeutic purpose. At the same time, due to the short range of the radiation, the effect on the surrounding tissues and other organs of the thyroid gland is minimal.
(131 iodine is a beta decay nuclide, T1/2=8.04 days, emitting beta rays (99%) and gamma rays (1%). beta rays have a maximum energy of 606.5 KeV, a maximum range of 3.63mm in the tissue, and an average range of 0.48mm. major gamma rays have an energy of 364 KeV and can be used for imaging.)
10.Which patients cannot be treated with radioactive 131 iodine?
Pregnant and lactating women who do not want to terminate their pregnancy
Those who plan to have a pregnancy within 6 months
Those who have not completely healed their wounds after thyroid surgery
Patients with WBC <3.0×109/L and severe liver and kidney dysfunction
Those who cannot comply with the radiation protection instruction
11.What preparatory work should be done before 131I treatment?
1）Elevate serum TSH level to >30mU/L by the following methods.
A Elevating endogenous TSH: withhold L-T4 for 4-6 weeks after total/near-total thyroidectomy or discontinue L-T4 for at least 3 weeks (for those who have started TSH suppression therapy).
B With recombinant human TSH: 2 consecutive days of intramuscular injection prior to clear thyroid treatment without discontinuing L-T4. rhTSH is particularly indicated for elderly DTC patients, those who cannot tolerate hypothyroidism and those who cannot achieve TSH targets after discontinuing L-T4. However, recombinant human TSH has not yet been registered and marketed in mainland China.
2) Iodine drug and diet abstinence for 3-4 weeks
3）Completion of neck ultrasound and routine laboratory tests, etc.
12.Will stopping Eugenol for 3-4 weeks before 131I treatment have any effect on health?
Discontinuing Eugenol can lead to hypothyroidism. Some patients may experience some symptoms of hypothyroidism, such as fear of cold and sweating, swelling, dry skin, weakness, slow reaction, memory loss, loss of appetite, bloating and constipation, abnormal blood sugar and lipid metabolism. However, discontinuation of eugenol is a necessary preparation for 131I therapy. In order to achieve the desired therapeutic effect, the patient needs to cooperate and temporarily overcome the short-term discomfort that may be caused by discontinuation of eugenol. Generally, if you resume taking Eugenol 24-48 hours after taking Iodine-131 treatment, the hypothyroidism can be corrected quickly.
13.How to perform 131I treatment? Is this treatment safe?
131I therapy is usually administered orally. After the patient has fasted for at least 2 hours, he/she should drink the liquid 131I diluted in warm boiled water at once orally in the isolation ward. Patients should drink an appropriate amount of water and urinate promptly after oral administration of 131I. During the isolation period, patients should avoid iodine diet, take rest and prevent colds. After treatment, patients should stay in a special radiation isolation ward for a period of time and be discharged only when the residual radioactive dose in the body has decreased to the prescribed standard. The isolation period is usually 3-5 days.
A single 131I treatment is relatively safe. For patients who require repeated treatment, there is no upper limit for the cumulative 131I treatment dose. As the number of treatments increases and the cumulative 131I dose increases, the risk of radiation side effects increases. Common side effects include chronic salivary gland damage, dental caries, nasolacrimal duct obstruction or gastrointestinal reactions, pulmonary fibrosis (requiring extended treatment intervals when the cumulative dose exceeds 1000 mCi), and bone marrow suppression (rare). there is no consistent conclusion on the relationship between 131I treatment and secondary tumors, and when the cumulative dose is too high (2000 mCi), the risk of radiation causing de novo primary tumors may exceed that of DTC itself. There is insufficient evidence that 131I treatment affects the reproductive system, but women are advised to avoid pregnancy for 6 to 12 months after treatment.
14. What is the dose of radioactive 131I treatment?
For the first “nail clearing” treatment, a fixed dose of 100mCi is usually used; for patients with lymph nodes in the neck or distant metastases, or patients with unexplained elevated Tg levels, the dose can be increased; for patients with more residual thyroid tissue or children, the dose should be reduced.
15.What are the side effects of 131I treatment? How to prevent and treat them?
Radiation inflammatory reaction (within 1~15 days after taking 131I): weakness, neck swelling and throat discomfort, dry mouth, salivary gland swelling and pain, change of taste, nasolacrimal duct obstruction, epigastric discomfort and even nausea, urinary tract damage, etc. are common. Prevention and treatment measures: give prednisone to prevent and relieve local edema; take acidic candy/Vit-C, chew sugar-free gum, massage salivary glands to reduce radiation damage to salivary glands. Reduce radiation damage to the pelvic and abdominal cavities by drinking more water, urinating more and taking laxatives.
Transient drop in white blood cells and platelets. Preventive measures: white-raising therapy.
Aggravation of underlying disease: Combination of other chronic diseases and/or advanced age patients with persistent hypothyroidism plus 131I injury, the underlying disease may be aggravated short-term. It should be closely observed and promptly treated
Psychological changes: Boredom, anxiety, insomnia, fear, etc. may occur. These psychological changes are not direct 131I injury, but originate from some factors of the treatment process (such as radiation protection isolation, aggravation of hypothyroidism and other disease effects, etc.). Prevention and treatment measures are based on psychological guidance.
16.What do I need to pay attention to after 131I treatment?
Close contact with pregnant women, infants and children is forbidden for 1 month after discharge, and other people should also have as little contact as possible and try not to go to public places.
You will need to take thyroid hormone replacement therapy (also TSH suppression therapy) for the rest of your life. Oral L-T4 is usually started (or resumed) 24 to 72 hours after nail clearing treatment.
Post-treatment 131I whole-body imaging is performed within 2 to 10 days after treatment.
17.Why is a whole body image required after radioactive 131 Iodine treatment?
Post-131 iodine therapy whole-body imaging can more accurately evaluate the severity of DTC and determine the indication for subsequent 131I therapy. The use of SPECT/CT to generate tomographic fusion images can help localize the lesion, distinguish physiological aggregates, and differentiate contamination, which can further improve the accuracy of diagnosis.
18.How to determine whether thyroid cancer has been cured? (Clinical cure criteria)
After surgery and iodine-131 treatment, all of the following conditions must be met at the same time to determine that thyroid cancer is cured.
1) No clinical manifestations (symptoms and signs) of the tumor.
2) absence of imaging manifestations of the tumor (including neck ultrasound and nuclear scan)
3) no 131I whole-body imaging after nail clearing treatment without thyroid bed and extra-bed tissue uptake of 131I
(3) After excluding the interference of autoantibodies (TgAb), serum thyroglobulin could not be measured in TSH suppressed state (i.e. Tg<1ng/mL) and Tg<2ng/mL in TSH stimulated state (3 weeks and more after stopping euthyroxine).
19.Why do I need to stop using Eugenol for a period of time when judging the efficacy?
On the other hand, TSH can promote the uptake of iodine 131 by tumor cells, which can better detect possible metastatic lesions when whole body iodine scan is performed to judge the efficacy of tumor treatment.
20.What are the main test indicators to be looked at during the follow-up after 131I treatment?
(1) TSH: In order to reduce the stimulating effect of TSH on DTC cells, the level of TSH should be reduced as much as possible. the goals of TSH suppression therapy are as follows.
2) Tg: After thyroid cancer postoperative +131I treatment, Tg has the highest sensitivity and specificity for determining DTC recurrence or residual in the absence of TgAb in the TSH-stimulated state. In DTC patients who have been completely clear of nail, the Tg cut-off values suggesting disease-free survival: in TSH suppressed state (basal state): <1ng/ml; after TSH stimulation (>30mU/L): <2ng/ml. In the absence of TgAb if Tg after TSH stimulation is <0.5ng/mLà suggesting 98%-99.5% possibility of tumor-free survival. (TgAb will bind to Tg and if TgAb is high, it will lead to a decrease in Tg measurement. Therefore, the effect of TgAb needs to be considered when measuring Tg)
21.Does 131I treatment need to be repeated?
Not necessarily. Repeat 131I treatment is needed in the following cases
(1) If there is still residual thyroid tissue after the first 131I treatment, the treatment goal of complete nail clearance is not achieved, and nail clearance treatment can be repeated.
(2) If metastatic foci of DTC (including local lymph node metastasis and distant metastasis) that cannot be removed surgically but have iodine uptake function are found after 131I treatment, 131I clearance treatment should be performed again.
22.What should be done after thyroid cancer recurrence?
23.After 131I treatment for thyroid cancer, if drug resistance occurs and 131I treatment cannot be continued, is there any other treatment method?
Chemotherapy and external irradiation are not recommended for thyroid cancer, DTC is not sensitive to chemotherapy drugs. The role of external irradiation in reducing the recurrence rate after surgery and 131I treatment is not clear. External irradiation therapy may be considered only in the following cases: 1. for local palliative purposes; 2. with residual tumors that are not visible to the naked eye and cannot be treated with surgery or 131I; 3. with painful bone metastases; 4. in critical sites that cannot be treated with surgery or 131I (e.g., spinal metastases, central nervous system metastases, certain mediastinal or subserosal lymph node metastases, pelvic metastases, etc.).
Patients with advanced DTC can consider using new targeted drugs when conventional treatment is ineffective and in a progressive state, among which tyrosine kinase inhibitors are more frequently used.
24.Do I need to abstain from iodine or low iodine diet after getting thyroid cancer?
The purpose of low iodine or no iodine diet before radioactive iodine therapy for thyroid cancer (at least 3 weeks) is to prepare for radioactive iodine therapy to reduce the intake of stable iodine, so that after radioactive iodine is given during the treatment, the thyroid cells and thyroid cancer cells, which are “starved” of iodine, will absorb radioactive iodine faster and more, and will eventually be more susceptible to radiation damage. This makes thyroid cells and thyroid cancer cells, which are “iodine starved” during treatment, absorb radioactive iodine faster and more, and are eventually more susceptible to radiation damage from radioactive iodine. A low iodine diet is defined as a daily intake of no more than 50 micrograms of iodine. A low iodine diet is not the same as a “no iodine diet”. Iodine and sodium are not related, so a low iodine diet is not the same as a “low sodium diet” either.
Patients with thyroid cancer are taking the drug Eugenol, which contains iodine. During the follow-up period after 131I treatment, a normal diet is sufficient, and there is no need for a strict iodine ban or low iodine diet.