BACKGROUND
Medullary thyroid cancer (MTC) is rare type of thyroid cancer that often runs in families. MTC is a more aggressive thyroid cancer and is more likely to spread outside the thyroid into the neck and to other parts of the body (distant metastasis) than the usual type of thyroid cancer (papillary thyroid cancer). Standard thyroid cancer treatment with radioactive iodine is not effective in MTC as the cancer cells to not take up iodine. Patients with MTC that has not spread outside of the neck undergo thyroidectomy to remove the thyroid and removal of the lymph nodes located close to the thyroid in the hope for a potential cure. However, there is limited data regarding the potential benefit of thyroidectomy on survival in patients with spread of the MTC outside of the neck when the cancer is diagnosed. This is seen in ~10% of patients with MTC and is associated with a poor prognosis (10-year survival rates of 40%).

This study used a population-based registry to 1) evaluate the prognosis based on the presence of what organs and how many contain MTC cells, 2) evaluate whether thyroidectomy is beneficial in these patients, and (3) identify the best candidates for thyroidectomy in patients with metastatic MTC at diagnosis.

THE FULL ARTICLE TITLE
Liu C-Q, et al. Survival outcome and optimal candidates of primary tumor resection for patients with metastatic medullary thyroid cancer. J Clin Endocrinol Metab 2024;109(11):2979-2985; doi: 10.1210/clinem/dgae214. PMID: 38570918.

SUMMARY OF THE STUDY
The study included 186 patients from the Surveillance, Epidemiology, and End Results (SEER) database diagnosed with MTC with distant metastasis between 2010 and 2020. The following information was extracted from the database for analysis: demographics (age, gender, race), cancer characteristics (grade, size, lymph node metastasis, distant metastasis), and type of treatment (thyroidectomy, neck dissection, radiation, and chemotherapy). The SEER database has data on five metastatic sites: lung, bone, liver, brain, and distant lymph nodes. The authors compared the survival outcomes of the thyroidectomy versus non- thyroidectomy group, including the overall survival (OS) and cancer-specific survival (CSS).

The average age at diagnosis of the study patients was 56 years, 56.5% being males. The percentage of patients with metastases was, as follows: bone 46%, liver 40%, lung 37%, distant lymph nodes 22%, and brain 5%. Overall, 58%, 30%, 10%, and 2% of the patients had 1,2,3, and 4 metastatic organs at diagnosis. Half of the patients had cancer spread to multiple organs. Slightly more than half of the patients (56.5%) underwent thyroidectomy. There was no difference between the thyroidectomy and non-thyroidectomy groups regarding age, gender, cancer size, metastatic organs and the number of organs involved. More patients in the non-thyroidectomy group had lung metastases, while more patients with lymph node involvement underwent thyroidectomy. More patients who underwent thyroidectomy also received chemotherapy.

Patients with single-organ metastasis had better OS and CSS as compared to those with 2 metastases, while there was no difference between patients with 3-5 organmetastases. The presence of brain metastasis indicated a significantly poorer OS and CSS as compared to other metastatic organs.

Overall, the thyroidectomy group showed improved OS and CSS as compared to the non-thyroidectomy group. The thyroidectomy group had ~1/3rd of overall risk of death and cancer-specific death than the nonthyroidectomy group. Patients with lung, bone, liver, and distant lymph node but not brain metastases had a better survival if they underwent thyroidectomy compared to the non- thyroidectomy group. Overall, chemotherapy and radiation did not improve survival.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
Overall, this study suggests that thyroidectomy may improve prognosis in MTC patients who have distant metastasis at diagnosis. Thyroidectomy may improve survival in MTC patients with a one- or two-organ metastases in the bone, lung, liver or distant lymph nodes at diagnosis. The survival may not improve in patients with brain metastases, who have a worse prognosis overall. Therefore, thyroidectomy may confer survival benefits in selected patients with metastatic MTC at diagnosis. Additional research is needed to confirm these findings before implementing them in the current guidelines for metastatic MTC treatment.

— Alina Gavrila, MD, MMSC

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