Recheck calcitonin after medullary thyroid cancer surgery
1.When should we start checking serum calcitonin after surgery? How often should it be checked? How long should it be continued?
Generally, our experience is to review the test once a month in the first six months, and then it can be changed to once every three months or six months. This is necessary for the follow-up of the patient.
2.Why are the reference values of calcitonin always different? For example, 0-100, 0-50, 0-10, 10-120?
The different reference values of calcitonin are mainly related to the method of measurement, but also to the reagents used for the measurement, the sensitivity of different methods and reagents is different. The reagents give corrected reference values. Even for the same reagent, the normal value may fluctuate slightly from batch to batch.
3.What is the relationship between the value of calcitonin and the size of the tumor?
In general, calcitonin values should be positively correlated with tumor size, but in some patients, there is no positive correlation between tumor size and calcitonin, and even calcitonin levels are within the normal range.
4. For patients with total thyroidectomy on both sides, does the presence of calcitonin indicate residual thyroid tissue (or residual cancer tissue)? Is there any relationship between the level of calcitonin and the amount of residue?
In 30% of patients with familial hereditary medullary carcinoma, calcitonin levels are in the normal range even when there are small metastases in the lymph nodes after surgery, and the same is seen in 50% of patients with sporadic medullary carcinoma who have some small residual lesions after surgery. Therefore, when looking at the so-called normal value, it must depend on the individual patient, and in general, the normal value is the 95 percent inclusion range of this measurement in the normal population, with some normal people being in the remaining 5 percent range. In contrast, normal values for calcitonin do not exist for patients, especially after surgery. Therefore, each patient should have an individual post-surgical calcitonin level as a “normal” reference value. Generally, the calcitonin level should be reviewed once a month for about six months after surgery, and the lowest value should be used as the patient’s normal post-surgical reference value. If the calcitonin level remains the same or is lower over time, the patient’s prognosis is good to some extent. However, if during the follow-up period, the patient has a short period of time in which the calcitonin level rises more than twofold, it indicates a recurrence and a possible poor prognosis.
5. How long does it take for calcitonin to return to normal after surgery? Will the value decrease slowly over time? What if it decreases slowly?
Generally, calcitonin starts to decrease one month after surgery, and it can drop to a relatively low level in about six months. The speed of decrease is related to the half-life of calcitonin production and metabolism in the body.
6.Does normal calcitonin mean that there are no cancer cells in the body?
The so-called normal value of calcitonin after surgery does not exist. Generally, the lowest point of calcitonin in the six-month test after surgery should be taken as the patient’s calcitonin level after surgery, which is a different concept from the level of calcitonin before surgery. At this point, if the calcitonin level is still measurable or comparable or higher than normal, it is important to determine whether there is tumor residual by the calcitonin elevation in the calcitonin stimulation test. It is necessary to do further examination or surgery.
7.How is calcitonin considered stable? Is a rapid increase within the normal range considered stable? Is a continuous increase within the normal range a sign of a bad development? Does it fluctuate up and down, and can it come down after it rises?
The stability of calcitonin is determined by two factors: firstly, if calcitonin is reduced to a level below the so-called normal value during the post-operative follow-up, and secondly, if it cannot be reduced to a level below the normal value, it is judged by the calcitonin stimulation test, which also indicates a stable calcitonin level if the stimulation test is negative. If there is a significant increase to more than twice the patient’s baseline level in a short period of time, metastasis or recurrence may have occurred and further testing is needed. It is possible that the disease is progressing in a bad direction. In general, it does not fluctuate from time to time, but if there are these fluctuations, we should pay attention to the trend of fluctuation, and the gradual upward fluctuation should also pay attention to the possibility of bad, if necessary, you can determine by calcitonin stimulation test, another factor is the test method has error instability, test quality control problems.
The currently recommended tests are.
(1) basal serum calcitonin.
(2) Stimulated serum calcitonin.
(3) Other serum markers of MTC such as CEA.
(4) Ultrasound and other imaging techniques.
(5) Fine needle aspiration cytology (FNA).
(6) Measurement of FNA for washout calcitonin.
(7) RET gene mutation detection.
8.Postoperative calcitonin decreased and then increased, is it metastasis? What could be the reason that it has been much over the standard after surgery?
If the calcitonin is elevated again after surgery, it is recommended to review it. If the result of review is still elevated, it is possible that it has recurred or metastasized. The first reason is that the calcitonin level was very high before surgery, and the short follow-up period after surgery may lead to the above problem, but the other reason is that the scope of surgery is not enough, or the lymph node dissection is not enough for residual tumor tissue or lymph node metastasis or distant metastatic lesions.
9.Is high calcitonin only related to the thyroid gland, but could it be caused by other diseases?
Generally, elevated calcitonin levels are associated with thyroid C cells, and may be elevated in tumors related to embryonic development, such as C-cell related teratoma.
10. Calcitonin continues to be elevated for many years after surgery, but there are no imaging indicators. Should I observe or reoperate?
If calcitonin continues to be elevated for many years but cannot be detected by ultrasound or CT, further testing is still needed. Currently, whole-body bone scans, PETCT examinations, etc. are recommended. It is usually possible to detect occult lesions, especially lymph node metastasis in the central region of the neck, mediastinal lymph node metastasis, etc. should be paid extra attention.