1. Radioactive iodine 131 is an important treatment for thyroid cancer after surgery Differentiated thyroid cancer, which accounts for about 90% of thyroid cancer, accounts for the vast majority of thyroid cancer. Why is it called differentiated thyroid cancer? Because it is similar to the original thyroid follicle in that they both secrete thyroid hormones and retain iodine uptake. The thyroid tissue relies on iodine and tyrosine to produce thyroid hormone, and thyroid cancer tissue, especially the differentiated type, including papillary and follicular carcinoma, can take in iodine, so we can use iodine for tracing and treatment of thyroid cancer tissue, which is radioactive iodine 131. 2. Which thyroid cancer patients can be treated with iodine 131? Differentiated thyroid cancer can be treated with iodine 131, but when thyroid tissue and thyroid cancer tissue are present at the same time, iodine cannot directly hit the thyroid cancer tissue. Because normal thyroid tissue has strong iodine uptake ability while cancerous tissue has weak iodine uptake ability, iodine 131 treatment is often a postoperative adjuvant treatment, i.e. when normal thyroid tissue is almost removed, thyroid cancer tissue can uptake iodine 131 like normal thyroid tissue at this time, so that it can enter the body for the purpose of treatment. This post-operative adjuvant treatment can be used for local recurrence of lesions or distant metastases, but if there is regeneration of thyroid tissue, iodine 131 will not achieve the expected purpose of fighting tumors. 3. Post-operative nail clearing treatment reduces recurrence rate Post-operative nail clearing treatment, as the name implies, is the treatment for the few thyroid tissues that cannot be cut off. Why should the normal thyroid tissue be cut off? Because it leaves behind the possibility of regrowth. What kind of tissue is prone to regrowth or recurrence? In the first case, if there are distant metastases, the thyroid gland must be destroyed by nail debridement in order to follow up with iodine 131 focal therapy. In some cases, extra-thyroidal invasion, such as invasion of the perineum, accumulation of fatty tissue or fibrous connective tissue around the thyroid gland, is more serious. However, no matter how experienced the surgeon is, it is impossible to remove all the thyroid tissue for fear of damaging the nerve tissue around the thyroid gland, so there will be remnants of the thyroid gland, and these remnants are part of the postoperative treatment, which is an important tool to reduce the recurrence rate. If nail clearing treatment is added after surgery, the thyroid tissue can be cleaned up more and the recurrence rate can be reduced. Firstly some lesions are cleaned up during nail clearing treatment, and secondly as a patient with differentiated thyroid cancer, if the tumor marker – thyroglobulin – is high, it can be determined that it is a metastatic site coming through. The benefit of nail clearing treatment is that no matter which cycle of thyroid cancer patients, if the treatment is completed, there is no tissue in the body that produces the thyroid gland, which facilitates long-term follow-up and centralized follow-up of patients. The completion of nail clearing treatment may take 1 or 2 sessions, but the benefits it provides are lifelong. Thyroglobulin is very sensitive and is a tumor marker for thyroid cancer. Without thyroid there is no globulin, or the globulin is at undetectable levels, and once the globulin is high it indicates that the patient has a recurrence. After the completion of thyroid clearing treatment, if iodine is used to visualize the whole body, it can be seen that there is no thyroid gland in the neck. If there are suspicious iodine uptake lesions in the normal gastrointestinal tract and urinary system, they are metastases. 4.How to monitor whether there is recurrence or metastasis after thyroid cancer surgery Thyroglobulin is an important marker of thyroid cancer after surgery and nail clearing treatment. Monitoring for recurrence and metastasis is usually done by monitoring serum, paying close attention to thyroglobulin, and thyroid hormone levels. In addition, ultrasound is a very important imaging tool to detect tumor recurrence and metastasis, which is non-invasive, safe and convenient. For example, lymph node metastasis in the neck is not reflected by globulin, but can be reflected very sensitively by neck ultrasound. For some serious patients, in addition to serum, blood, ultrasound and detection means, whole body imaging with iodine 131 can be used to observe where the iodine ingested into the body goes, and if it goes somewhere else when there is no thyroid, it is a suspicious sign of metastasis. There are some lesions that need to be prevented. These lesions do not take in iodine and are poorly differentiated, so how can they be tracked? At this time, we can use the more advanced positron emission computed tomography in nuclear medicine to detect the glucose metabolism of the lesions, which can also be used to detect the recurrence of the lesions, and sometimes tumor-positive imaging agents are used to detect the presence of the lesions. There are also imaging, such as CT and MRI, which can help detect metastases and suspicious lesions of thyroid cancer. All these are important auxiliary means to detect tumor recurrence after surgery. 5.Gene detection for individualized and precise treatment of thyroid cancer Gene detection is an important part of targeted therapy driven by molecular features. Precision medicine is driven by molecular features. Thyroid cancer is related to it, when there are mutations in BRAF gene, the mutation rate can reach 40% to 70%, or even 80%. There are also mutations in some RAS genes, such as NRAS, and ret gene rearrangement detection. In clinical practice, BRAF genotype mutation, RAS gene rearrangement detection, and EGF are commonly used, and these are the directions we are exploring. Recently, it has been found that patients with BRAF mutations have a significantly higher rate of local recurrence, higher rate of lymph node metastasis, and higher risk of death, which is a mainstream internationally. A recent study showed that the risk of death in such patients with BRAF mutations is about 2.66 times higher than that without the mutation. In addition, with a mutation in the NRAS gene, the follicle may be prone to metastasis, and the BRAF gene may not heal well after a mutation. The results of the study showed that patients with BRAF mutations had significantly reduced iodine uptake in distant metastases. The implication of this study is that in patients with distant metastases, a genetic test can be performed to detect whether the gene is mutated, and if so, iodine 131 will not be effective in such patients with metastases. Once this occurs, it is possible to pre-treat with differentiation-inducing drugs to buy time for subsequent treatment, or to change the treatment early, or to add adjuvant drugs to change the uptake status. Genetic testing can also predict some recurrences and metastases. BRAF gene mutation, after relapse, also has a high rate of metastasis in the cervical lymph nodes and a high capacity for recurrence, so to have a BRAF gene mutation, even though there is no distant metastasis, it is necessary to actively pursue nail clearing therapy. Genetic testing guides a series of processes, guides postoperative adjuvant therapy, and can guide the scope of surgery, which is also a guiding direction for individualized and precise treatment of patients.