According to the data, thyroid cancer accounts for 1.4% of diagnosed tumor patients, with an incidence rate of about 2.39/100,000 and a mortality rate of 0.2% of tumor patient deaths. It may be related to the improvement of health care level, the development of large-scale physical examination, and the development of imaging technology such as ECT, which makes the detection rate of thyroid tumor increase. The ratio of male to female incidence is about 1:2 to 1:3, and it can occur in all age groups.
There are two types of tumors according to their cellular origin. Papillary thyroid carcinoma, follicular thyroid carcinoma and undifferentiated carcinoma are among those that originate from follicular cells of the thyroid gland. Papillary thyroid carcinoma and follicular carcinoma are also known as differentiated thyroid cancer (DTC), and tumor tissue containing both papillary and follicular carcinoma components is classified as mixed carcinoma. DTC is mainly treated by surgery, after which 131I is used to remove the remaining thyroid tissue and uncleared metastatic lymph nodes, followed by thyroid tablets to replace the thyroid function, which can prevent recurrence and metastasis or late recurrence and metastasis, prolong patients’ survival and improve their quality of life. survival period and improve the quality of patients’ survival.
I. Treatment principle and significance
The residual thyroid tissue or possible metastases after DTC surgery has the function of 131I uptake. 131I releases β-rays when decaying, and its internal irradiation can remove the residual thyroid gland very effectively. After the residual thyroid tissue is completely removed, the TSH level rises, which facilitates the early detection of DTC metastases and further treatment of DTC metastases with 131I; whole-body imaging after the removal of 131I can often reveal DTC lesions that are not revealed by the diagnostic dose of 131I imaging, which is important for the development of patient follow-up and treatment plans. The side effects or adverse reactions are minimal when the patient is treated because all normal cells in the body do not absorb 131I and do not kill normal cells.
Indications and contraindications
1. All patients with DTC who have residual thyroid tissue after surgery, whose 131I uptake rate is greater than 1%, and who have residual thyroid tissue in the thyroid bed on thyroid imaging, should use 131I to remove residual thyroid tissue.
2.Patients with DTC who have undergone surgical removal of the primary foci and 131I to remove the residual thyroid tissue, and who have recurrent foci or metastases that cannot be surgically removed, and who have a focal concentration of 131I on 131I imaging, and who are in good general condition.
3.Patients with DTC whose residual thyroid tissue has been completely removed, if other examination methods (X-ray examination, ultrasound examination, etc.) do not find any DTC lesions in the body, and the 131I image is negative, but the Tg level is elevated (equal to or greater than 10μg/L), which is highly suggestive of diffuse microscopic DTC lesions in the body, is an indication for treatment with 131I.
4. Contraindications Pregnant and lactating patients; postoperative wounds that have not healed; patients with WBC below 3.0X109/L; patients with severe impairment of liver and kidney function.
III. Preparation before treatment.
In order to ensure that DTC cells fully absorb more 131I , taking (eating) food and drugs containing iodine must be strictly prohibited before treatment. Even consuming a small amount of seafood or disinfecting the skin with iodine for injection can increase the content of non-radioactive iodine in the patient’s body, and DTC cells are easily saturated with these non-radioactive iodine. Tumor cells that are “full” of non-radioactive iodine will absorb little or no more of the 131I subsequently given, making the therapeutic effect much less effective. Therefore, a very strict ban on iodine intake prior to treatment is essential, including the use of non-iodized salt and non-iodized soy sauce in stir-fries instead of the iodized refined salt and common soy sauce available in the market. Thyroid tablets contain a large amount of non-radioactive iodine, so it is also important to stop taking thyroid tablets before treatment as prescribed by your doctor. However, common chicken, duck, beef and mutton, eggs and vegetables, and freshwater fish are not included in the ban. Forty-five days before each 131I treatment, iodine intake should be strictly prohibited, while thyroid tablets should be stopped and T3 capsules (1 pill, 25ug, twice a day) should be taken instead for 30 days, and T3 capsules should be stopped 15 days before treatment. The feeling of weakness after stopping T3 does not require treatment and will disappear after resuming the medication.
IV. Treatment
1. After taking 131I orally, patients must be hospitalized in isolation for observation. Each patient should live in a single room in isolation, and should not go out to activities and try not to be close to others or staff to reduce the chance of irradiating others. Routine measurement of blood, urine and stool, fasting blood glucose, liver and kidney function tests. Make X-ray chest film, electrocardiogram, neck and abdominal ultrasound. Check T3, T4, rT3, FT3, FT4, TSH, Tg, TgA, TMA, determine thyroid uptake 131I rate line, thyroid SPECT imaging.
2, the day of preparing to take 131I to a week after taking 131I, patients can be given oral prednisone 10mg 3 times / d to reduce the local edema caused by the radiation effect due to the large amount of 131I concentrated in the thyroid gland, especially laryngeal edema. After taking 131I, it is advisable to drink more water and evacuate urine in time to reduce bladder and whole body irradiation. Ask the patient to defecate at least once a day to reduce the damage to the intestine caused by radiation. After taking 131I, patients are advised to melt VitC tablets in their mouths or chew gum and other acidic foods frequently to promote saliva secretion and prevent or reduce damage to salivary glands from radiation. 131I treatment should be followed by contraception for one year for female patients and six months for male patients.
3. Treatment dose, 131I 3.7GBq (100mCi) is routinely given. If a functional metastatic lesion has been found before removal, the 131I dose can be 5.55-7.40GBq (150-200mCi) to play the role of removing residual thyroid tissue while treating the metastatic lesion. If there are too many residual thyroid tissues after surgery or the rate of 131I uptake by residual thyroid tissues is high (more than 30%), the removal dose can be considered to be appropriately reduced to alleviate the local reaction caused by taking 131I.
4.Whole body imaging is performed 5-7 days after taking 131I, when it is possible to find DTC metastases that are not detected by diagnostic dose of 131I imaging, which provides a basis for further follow-up and treatment plan development.
5. After removal of treatment, thyroid hormone should be routinely given to patients. One is to play a replacement role to keep the body in a normal metabolic state; on the other hand, exogenous thyroid hormone can inhibit the secretion of TSH in the body, and then achieve the effect of inhibiting the growth of DTC cells. If the patient has more residual thyroid tissue after surgery, thyroid hormone can be given starting 1 week after taking 131I; if the patient has starred symptoms and signs of hypothyroidism before removing the treatment, thyroid hormone can be given starting 4 hours after taking 131I. The dose is generally 40mg of thyroid tablets or L-T450μg, 3 times/d. The dose can be adjusted according to the serum thyroid hormone level and TSH level, so that the TSH can keep the low limit of normal level or slightly below the normal level in order to play the role of inhibitory treatment.
6.Radiological protection Because of the high dose of 131I used to treat DTC patients, special attention should be paid to radiological protection. Patients have one ward per person, and there is a separate special bathroom in the ward. The patient’s clothes and bedding should be placed for certain decay treatment and separate washing. Medical staff should have protective facilities (such as lead screens) for patient observation, especially within 3 days after taking 131I, and should try to be prepared in advance so that the contact time with the patient can be shortened. While paying attention to radiation protection, medical personnel should also pay attention to reducing the adverse effects caused psychologically to the patient. Patients can be discharged with a 131I retention level equal to or less than 1.11 GBq (30 mCi). Generally, the amount of 131I retained in the body can be less than 1.11GBq after 3 days of taking 131I.
7. Treatment reaction and treatment: It can be divided into local reaction and systemic reaction according to the site of occurrence. The majority of patients feel weakness, poor appetite, abdominal distension and nausea 1 to 2 days after taking 131I orally, and some patients may experience vomiting, diarrhea and headache. Patients with DTC who have residual thyroid tissue removed with 131I after surgery, especially those with more residual thyroid tissue, often experience swelling and pain in the anterior neck area, which may even involve the upper part of the chest. Dyspnea due to laryngeal edema is rare, and if it occurs, prednisone can be given orally, and in severe cases, dexamethasone drip can provide rapid relief. The salivary glands may also show mild swelling and pain. Paying attention to oral hygiene and using methods to promote salivary secretion can prevent or reduce damage to the salivary glands from radiation. Most of the above local early reactions will resolve on their own in about 1 week. In patients with DTC with diffuse lung metastases, repeated treatment with high-dose 131I may lead to radiation pneumonia or pulmonary fibrosis, so the dose of 131I for each treatment should be controlled to less than 2.96 GBq (80 mCi) in the patient’s body after taking 131I for 48 hours. Bone marrow suppression is rare, and a transient decrease in white blood cells and platelets may be observed. Most scholars believe that the incidence of leukemia in patients with DTC treated with 131I is similar to that of the natural population, but high-dose 131I therapy should not be given frequently. gasara et al. studied 1064 women of childbearing age treated with 131I for DTC, 111 of whom had one or more pregnancies after treatment, and 134 babies were born, all of whom were found to have significant abnormalities. Sarkar et al. followed 40 patients with DTC who received an average of 17.4 GBq of 131I for 6 to 20 years and found that the incidence of infertility, miscarriage, preterm delivery or genetic defects was not different from the general population. Schlumberger et al. observed 2133 pregnancies in 1877 women of childbearing age with DTC and analyzed the effect of radioiodine treatment on pregnancy, receiving The results showed that there was a higher rate of miscarriage in pregnancies within 1 year after treatment, but the incidence of preterm delivery, stillbirth, low birth weight or congenital anomalies did not differ from the normal population. Whether the increased rate of miscarriage within 1 year was due to abnormal thyroid function or was related to 131I treatment needs further study.
V. Evaluation of efficacy
1.Effect evaluation of removal treatment: When the patient’s serum thyroid hormone level is lower than normal and TSH is higher than normal, the rate of 131I uptake in the thyroid bed is less than 1%, and no thyroid tissue is visualized in the diagnostic dose of 131I thyroid imaging, those who meet these two conditions are completely removed. Otherwise, the removal is complete.
2.Follow-up: Generally, follow-up visits should be conducted 3-6 months after treatment to evaluate the removal effect. If the thyroid gland is completely removed at the previous follow-up and no additional functional metastases are found, the follow-up should be done after 1 year; if the thyroid gland is still negative after 1 year, the follow-up should be done after 2 years; if the follow-up is negative after 2 years, the follow-up can be done every 5 years afterwards. Routine physical examination, X-ray chest radiograph, serum TT3, TT4, TSH, Tg, TgA measurement, thyroid iodine uptake rate measurement and 131I whole body imaging should be performed at each follow-up visit. Thyroid hormone should be discontinued for 4-6 weeks prior to follow-up so that TSH is elevated.
3. Repeat treatment: If incomplete removal of residual thyroid is found at follow-up or functional metastases are found, further treatment with 131I is indicated.
4.Factors affecting the efficacy: Different case types of differentiated nail cancer and the patient’s age have no significant effect on the type of removal. And gender, 131I dose, residual thyroid size, high or low iodine uptake rate of residual thyroid, and whether there are functional metastases outside the thyroid gland are the factors affecting the efficacy. The reported data showed that the primary complete removal rate was 84.2% for female patients and 65.5% for males; the complete removal rate was 63.3% for 131I doses less than 3.7 GBq (100 mCi) and 85.3% for those equal to or greater than 3.7 GBq; the primary complete removal rate was 91.7% for 131I uptake rates less than 10%, 11%-30% group 76.8%, and 51.4% in the >31% group. The primary complete removal rate was only 26.1% for patients with functional metastases and 93.9% for those without functional metastases. Another common clinical factor affecting the removal effect is that the patient’s ability to take up 131I in residual thyroid tissue is reduced due to lax iodine avoidance or insufficient time to stop using thyroid hormone.
5. Long-term efficacy evaluation: The efficacy of 131I treatment of DTC metastases is encouraging. After a few courses of treatment, 1/3 of patients can be “cured” and survive for more than 20 years; 1/3 of patients with recurrence within 10 years can be retreated and most patients can be “cured”. 1/3 of patients have poor outcome due to various factors. Most of the patients can be “cured”. 1/3 of the patients have poor outcome due to various factors. The efficacy of systemic distant metastases of differentiated thyroid cancer such as lung, bone, liver and other organ metastases depends on the severity of metastasis, the location of metastasis and the impact on the function of metastatic organs. Generally, the dose of 131I should be increased, and the density and frequency of treatment should be increased. After active treatment, most patients can be significantly relieved, their symptoms can be reduced or gradually disappear, and their quality of life can be significantly improved. Individuals with few metastases and high 131I uptake can even be “cured”.
Suggestions for clinical surgeons
DTC patients are mainly treated by surgery, and the survival period after surgery is long, but the recurrence rate is 32% if treated by surgery alone; 11% if treated by surgery plus thyroid hormone; 2.7% if treated by surgery, 131I and thyroid hormone. The mortality rate of patients with DTC treated with surgery alone is 3.8 to 5.2 times higher than that of surgery plus 131I treatment. Therefore, the choice of treatment plan directly affects the patient’s prognosis. Therefore, it is recommended that when a surgeon operates on such a patient, he or she should try to completely remove the normal thyroid tissue, including the glandular envelope, while removing the primary thyroid cancer, because the presence of a small amount of normal gland will inhibit the uptake of 131I by the cancer cells (the principle of competitive inhibition). Because of the traditional surgical practice of removing thyroid cancer tissue, it is customary to leave some normal thyroid tissue in the body. This traditional treatment has only disadvantages for patients with existing metastases or unclearly cut cancer foci. In fact, preserving some normal tissue does not eliminate the need for lifelong postoperative thyroid hormone replacement therapy, and risks the presence of residual cancer in the preserved gland. Therefore, for patients with DTC confirmed by intraoperative frozen section, the primary cancer foci should be excised along with the envelope to create conditions for further 131I treatment, and patients and their relatives should be informed of further comprehensive treatment measures, such as surgery, 131I and thyroid hormone treatment, which is the new trend of comprehensive treatment for DTC at home and abroad.