Clinical Thyroidology® for the Public
Summaries for the Public from recent articles in Clinical Thyroidology
Table of Contents | PDF File for Saving and Printing
THYROID CANCER
The role of thyroglobulin testing in identifying cancer return after lobectomy
BACKGROUND
Thyroid surgery is necessary to treat most cases of thyroid cancer. Often, removing just that part of the thyroid gland (called a thyroid lobectomy) that contains a thyroid cancer is enough to fully treat this disease. Unfortunately, thyroid cancer can come back after thyroid surgery, sometimes months or years later. For this reason, people diagnosed with thyroid cancer must be carefully monitored for cancer recurrence (return) after thyroid surgery. One way of doing this might be to regularly check the blood levels of a protein called thyroglobulin (Tg), which is only made by thyroid cells, including both normal and cancerous thyroid cells. In general, the more thyroid tissue (or thyroid cancer) present, the more Tg will be made. So, if a thyroid cancer recurs after thyroid surgery, the blood Tg levels may be elevated or may rise as the recurrent cancer grows. In addition, some people may develop an immune system response to Tg by making antibodies to this protein (TgAb). Like Tg, TgAb is detectable in the blood and, because the TgAb level should follow the Tg level (that is, higher Tg levels should mean higher TgAb levels), TgAb levels might also rise if thyroid cancer recurs.
Monitoring Tg levels works the best if the patient had a total thyroidectomy, where most of the thyroid tissue is removed. In patients that have had a lobectomy, they still have a lot of normal thyroid tissue left, all of which produces Tg. It is not clear how the high the Tg or TgAb levels must be, or how much these levels must rise after surgery, to correctly predict thyroid cancer recurrence in patients that had a lobectomy. In fact, several previous studies found that neither blood Tg nor TgAb levels predict thyroid cancer recurrence after thyroid lobectomy.
The research described here studied blood Tg and TgAb levels at specific time points after thyroid lobectomy among patients diagnosed with thyroid cancer. This was done to see if there is a particular Tg and/or TgAb blood level, or rise in these levels over time, that can correctly predict thyroid cancer recurrence.
THE FULL ARTICLE TITLE
Siyuan Xu et al 2021 Predictive value of serum thyroglobulin for structural recurrence following lobectomy for papillary thyroid carcinoma. Thyroid 31:1391–1399.
SUMMARY OF THE STUDY
The authors of this study looked at blood Tg and TgAb levels over time in 1852 people who underwent thyroid lobectomy to treat the most common type of thyroid cancer (papillary thyroid cancer). Blood Tg and TgAb levels were measured after surgery for each person twice each year for five years and then once yearly. Imaging studies were used to identify which people in the study developed cancer recurrence and mathematical/statistical testing was used to see if the blood Tg and/or TgAb levels could have predicted such recurrence. Overall, the authors found that the risk of thyroid cancer recurrence was significantly increased if the first blood Tg level tested was 5.3 mg/mL or higher, or if the last blood Tg level tested was 11mg/mL or higher. A sudden increase in blood Tg level was also associated with thyroid cancer recurrence. In contrast, thyroid cancer recurrence was not related to blood TgAb levels or changes in blood TgAb levels over time following surgery.
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
The study authors found that blood Tg levels tend to be higher, or to rise more suddenly, when thyroid cancer recurs after treatment with thyroid lobectomy. These findings suggest that regular checks of the blood Tg level after thyroid lobectomy could help identify thyroid cancer recurrence. This could lead to earlier treatment for recurrent thyroid cancer, thus potentially preventing such cancer from growing and/or eventually spreading to other parts of the body. Additional studies involving many more patients are needed to confirm these findings and to better define if blood Tg levels can help predict thyroid cancer recurrence after thyroid lobectomy
— Jason D. Prescott, MD PhD
ATA THYROID BROCHURE LINKS
Thyroid Surgery: https://www.thyroid.org/thyroid-surgery/
Thyroid Cancer (Papillary and Follicular): https://www.thyroid.org/thyroid-cancer/
ABBREVIATIONS & DEFINITIONS
Papillary thyroid cancer: the most common type of thyroid cancer. There are 4 variants of papillary thyroid cancer: classic, follicular, tall-cell and noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP).
Partial thyroidectomy: surgery that removes only part of the thyroid gland (usually one lobe with or without the isthmus).
Lobectomy: surgery to remove one lobe of the thyroid.
Thyroglobulin: a protein made only by thyroid cells, both normal and cancerous. When all normal thyroid tissue is destroyed after radioactive iodine therapy in patients with thyroid cancer, thyroglobulin can be used as a thyroid cancer marker in patients that do not have thyroglobulin antibodies.
Antibodies: proteins that are produced by the body’s immune cells that attack and destroy bacteria and viruses that cause infections. Occasionally the antibodies get confused and attack the body’s own tissues, causing autoimmune disease.
Thyroglobulin antibodies: these are antibodies that attack the thyroid instead of bacteria and viruses, they are a marker for autoimmune thyroid disease, which is the main underlying cause for hypothyroidism and hyperthyroidism in the United States.
Cancer recurrence: this occurs when the cancer comes back after an initial treatment that was successful in destroying all detectable cancer at some point.
AMERICAN THYROID ASSOCIATION® , ATA® , THYROID® , CLINICAL THYROIDOLOGY® , and the distinctive circular logo are registered in the U.S. Patent and Trademark Office as trademarks of the American Thyroid Association® , Inc.© 2024 American Thyroid Association.
