While thyroid cancers are among of the most common types of cancers worldwide (with a global incidence of 600,000 new cases per year), medullary thyroid carcinoma (MTC) consists of only 1% to 2% of all thyroid malignancies, making it the rarest subtype of this cancer. 

“Unlike in differentiated thyroid cancers, the low incidence and a limited number of large-scale studies of MTC have resulted in a paucity of high-quality evidence to reach a consensus on diagnosis and treatment,” Jayasinghe and colleagues wrote in the Journal of International Medical Research. 

Nevertheless, physicians benefit from guidelines periodically issued by trusted medical bodies, such as the American Thyroid Association; their evidence-based recommendations guide the direction of MTC care around the world. 


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Surgical Care 

Surgery has always been an integral part of MTC treatment protocols. The aim of surgery is twofold: extending disease-free survival and preventing locoregional recurrence. 

A patient who is assessed to be a suitable candidate for surgery usually undergoes total thyroidectomy and bilateral cervical neck lymph node dissection. Current guidelines recommend compartment-oriented lymph node dissection of other involved cervical lymph node basins; less clear is how uninvolved lateral neck lymph node basins should be approached, especially in patients with very high calcitonin levels. 

Read more about MTC etiology 

“For patients with basal serum calcitonin >200 pg/mL, contralateral lateral neck dissection should be considered if ipsilateral lateral neck lymph nodes are involved,” Barta-Kurycki and colleagues wrote in Therapeutic Advances in Endocrinology and Metabolism. 

However, there is a lack of scientific consensus regarding whether the dissection of lymph node compartments changes clinical outcomes if the patient does not display any evidence of neck lymphadenopathy or distant metastases. 

If we are to look at the evolution of surgical treatment for MTC over the years, we see that surgical decisions increasingly favor total thyroidectomy and lymph node dissection. Statistically, the number of lymph nodes removed per dissection has increased. The rationale behind these actions is that “you can never be too careful,” and surgeons would much rather overdo things slightly rather than miss 1 small patch and have to do the surgery twice, which increases the risk of iatrogenic infection.

Nevertheless, the extent of lymph node dissection deemed adequate remains a source of lively debate. A study with 316 patients demonstrates that the performance of lymph node dissection without evidence of structural disease has no additional benefit to the patient in terms of reducing recurrence or improving survival. 

However, surgeons are rightfully concerned about the risk of recurrence for 2 main reasons: it may mean that the initial surgery was not thorough enough, suggesting that the situation could have been avoided; and second, the psychological effect of a patient being told that they have cancer again can be devastating. 

For years, cancer research has focused on identifying patterns of recurrence and establishing any factors, modifiable or not, that may contribute to an increased risk of recurrence. As our knowledge of these matters improves, patients diagnosed with cancer early may have a real shot at living free of recurrence after initial treatment. 

Prophylactic Surgery 

We are living in the genetic age, in which genetic testing is faster, cheaper, and more reliable than it has ever been. As such, it is entirely possible for patients to be aware that they have inherited germline mutations in the RET protooncogene, even without/before the manifestation of signs and symptoms. 

For this group of patients, prophylactic thyroidectomy may be a reasonable course of action. The American Thyroid Association proposes a risk stratification system to determine which group of individuals should be given priority access to prophylactic thyroidectomy—patients who are at the highest risk category tend to have MEN 2B syndrome and the M9189T RET mutation. 

“Prophylactic thyroidectomy is performed with the intention of minimizing long-term morbidity and mortality associated with MTC,” Jayasinghe and colleagues wrote. “Those in the highest-risk category are considered for total thyroidectomy with [central neck dissection] within the first year of their life.” 

All patients who pass a certain threshold of risk, if not offered prophylactic surgery, should be under close medical surveillance with regular check-ups (at least once a year). If a patient’s risk goes up following subsequent visits, surgeons should use their best judgment on whether to offer prophylactic surgery as a precautionary measure against tumor growth. 

Read more about MTC prognosis 

As with any surgical procedure, the careful collection of evidence can help surgeons refine their patient selection protocol and improve overall outcomes. In light of this, medical researchers must continue to acquire data to compare different types of surgeries and their outcomes, despite the rarity of the disease.

“The wide spectrum of tumor biology with substantial variability in clinical practice has led to a lack of consensus regarding the diagnosis and surgical management of these tumors,” Jayasinghe et al wrote. ”Further research is essential regarding determining the extent of neck dissection, risk stratification, and the optimum use of tumor markers in therapy.” 

References

Jayasinghe R, Basnayake O, Jayarajah U, Seneviratne S. Management of medullary carcinoma of the thyroid: a reviewJ Int Med Res. Published online July 12, 2022. doi:10.1177/03000605221110698

Bartz-Kurycki MA, Oluwo OE, Morris-Wiseman LF. Medullary thyroid carcinoma: recent advances in identification, treatment, and prognosisTher Adv Endocrinol Metab. Published online October 8, 2021. doi:10.1177/20420188211049611