State of the art and future directions in the systemic treatment of medullary thyroid cancer

Neoadjuvant Treatment in Locally Advanced Thyroid Carcinoma

Although the focus in the last decades has been on the overdiagnosis of incidentally detected thyroid carcinomas in early stages, the other extreme of the disease is represented by locally advanced tumors with the invasion of neighboring structures. These are infrequent tumors, but they have a high complexity and a poor prognosis. In the absence of effective therapies allowing preoperative tumor reduction, in order to achieve a more restricted surgery, treatment was limited to aggressive surgery with resection of the aerodigestive tract and major vascular structures or palliative treatment. However, due to the increased knowledge of tumor biology and the results that tyrosine kinase inhibitors have achieved in the treatment of radioactive iodine-refractory tumors, neoadjuvant therapy with a curative intent has emerged as a reality to be taken into account when dealing with these patients. This paper presents a narrative review of the current scientific evidence regarding neoadjuvant treatment in locally advanced thyroid cancer.

Is Encapsulated Medullary Thyroid Carcinoma Associated With a Better Prognosis? A Case Series and a Review of the Literature

Context

Medullary thyroid carcinoma (MTC) is a malignant neuroendocrine neoplasm that may spread to lymph nodes before the primary tumor is diagnosed; moreover, distant metastases are already present in about 10% of patients at diagnosis. Serum calcitonin (Ctn) usually reflects the spread of disease, thus orienting the extent of surgery and predicting the possibility of biochemical remission. Tumor size and vascular invasion are important prognostic factors, but little is known on the relationship between other histopathological features, such as the presence of a tumor capsule, and long term outcome of MTC.

Purpose

To evaluate the prevalence of encapsulated tumors among MTCs and the association of tumor capsule with a favorable outcome after surgery.

Methods

A retrospective observational single-center study was conducted together with a narrative review of the available literature.

Results

Among 44 patients (27 female, 17 male; median age: 56 years) with MTC (6 hereditary, 37 sporadic) followed up at our center in the last four years (median follow-up: 29.2 months), seven (15.9%) showed an encapsulated tumor at histology and a clinical remission after surgery. None of them had nodal metastases and median preoperative Ctn (398 pg/mL, IQR 126.5-7336) did not differ significantly from that of the 14 patients (31.8%) with persistent disease after surgery (787 pg/mL, IQR 340.5-2905.5; p=0.633), although their tumor size was significantly higher (median 33 mm versus 16 mm respectively, p=0.036). Among patients with preoperative Ctn levels above 500 pg/mL (n=11), only two (18.2%) showed undetectable Ctn levels during follow-up, both having an encapsulated MTC (OR 0.000, p=0.02). Notably, they were two similar cases of large MTC (> 3 cm) with extensive hyalinization and calcification, associated with very high Ctn levels (> 13'500 and 1'100 pg/mL, respectively) but no nodal nor distant metastases, in complete remission after surgery although one of them carried the aggressive M918T somatic RET mutation.

Conclusion

MTC rarely shows a tumor capsule, which seems to correlate with a better prognosis and absence of nodal metastases, regardless of RET or RAS mutational status. Among encapsulated MTCs (E-MTC), Ctn levels and tumor size are not predictive of persistence of disease after surgery.