BACKGROUND
Medullary thyroid cancer (MTC) is a relatively rare cancer type that can develop in a person’s thyroid gland, a butterfly shaped organ located in the front of the neck. The thyroid gland makes a critical hormone, called thyroid hormone, that controls a person’s energy balance (metabolism). There are two forms of MTC; hereditary MTC (inherited), in which multiple family members will develop this cancer because of increased risk in their family, and sporadic MTC, which is not inherited and so develops without increased risk of this cancer in associated family members. MTC often already involves multiple areas of the thyroid gland at the time it is first diagnosed (called multifocality) and it may also have already spread out of the thyroid into neighboring neck lymph nodes. For these reasons, to completely remove this cancer, surgery to take out the entire thyroid gland (called a total thyroidectomy), as well as the neck lymph nodes located next to the thyroid (called a prophylactic central neck dissection) is generally recommended.

Recent studies have shown that, for some other types of thyroid cancer, removing just that part of the thyroid where the cancer is located (called a thyroid lobectomy) is as good as removing the entire thyroid gland for treatment. Moreover, thyroid lobectomy has a lower risk of complications than does total thyroidectomy. Finally, the remaining thyroid tissue left behind after a thyroid lobectomy will continue to make at least some thyroid hormone (which must be taken as a pill every day of a person’s life after surgery if total thyroidectomy is performed). On the other hand, if only part of the thyroid is removed, cancer may be left behind in the part of the thyroid that remains or might develop in this remaining tissue at some point in the future. The goal of the study described here was to test whether thyroid lobectomy alone, instead of total thyroidectomy with central neck dissection, might be safe and effective treatment for people diagnosed with MTC.

THE FULL ARTICLE TITLE
Cappagli V et al. Multifocality and bilaterality in medullary thyroid cancer: basis for a proof-of-concept safety of lobectomy. Eur Thyroid J 2025;14(5):e250074

SUMMARY OF THE STUDY
The authors studied 389 people diagnosed with MTC who underwent total thyroidectomy, with central neck dissection, at their hospital between 2005 and 2018. In each case, the removed thyroid gland was examined to see if multifocal cancer was present and genetic testing was performed to see if the MTC for each patient was hereditary or sporadic. All patients in the study were followed over time with neck ultrasound imaging and blood testing to see if they were cured after surgery or if MTC subsequently returned (called recurrence).

The study results showed that multifocal MTC was present 22% of the time, overall, after total thyroidectomy. Hereditary MTC was identified for 78 of the 389 patients and, for the hereditary MTC patients, multifocal MTC was much more likely to be present (56.4%) than for patients diagnosed with sporadic MTC (14.5%). Although approximately 66% of the study patients were found to be cured after surgery, multifocal MTC was found to be associated with more aggressive MTC, including direct spread out of the thyroid into surrounding tissues and spread to neighboring lymph nodes, as well as incomplete cancer removal during surgery.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
The results of this study suggest that there may be a subgroup of sporadic MTC patients for whom thyroid lobectomy would be a safe and effect treatment option. Unfortunately, this study was unable to identify any preoperative characteristics among the sporadic MTC patients studied that would predict which of these patients would be adequately treated with thyroid lobectomy alone. The study results are additionally useful for decision making among patients who undergo thyroid lobectomy for reasons other than MTC and for whom sporadic MTC is then discovered when the removed thyroid lobe is evaluated by a pathologist after surgery. Specifically, these data suggest that if such an unexpected MTC is small, completely contained within the removed thyroid tissue and there is no evidence of multifocality, additional surgery to remove the remaining thyroid tissue (called a completion thyroidectomy) may be safely avoided in favor of monitoring for future MTC recurrence. Finally, given the high rate of multifocality found for cases of hereditary MTC, this research confirms that total thyroidectomy remains the appropriate treatment for such cases.

— Jason D. Prescott, MD PhD

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