Endocrine Abstracts

JOINT3736

Introduction: Medullary thyroid carcinoma (MTC) accounts for up to 5% of thyroid carcinomas and can exhibit variable clinical behaviour. Nearly 25% are associated with multiple endocrine neoplasia type 2 syndrome (MEN2) or familial isolated MTC.

Objectives: To evaluate the characteristics and clinical evolution of patients with MTC followed at our institution.

Methods: Retrospective analysis of the medical records of patients diagnosed with MTC between 2009 and 2024.

Results: Seventy-six patients were identified (55.3% women), with a mean age at diagnosis of 61±14.1 years. Preoperative diagnosis was established in 32.9% (n = 25) of patients. At diagnosis, staging was as follows: stage I (n = 32), II (n = 15), III (n = 6), IVa (n = 15), and IVc (n = 8). Germline pathogenic RET variants were identified in 14 of 67 patients (20.9%), while somatic variants were identified in 8 of 15 patients (53.3%). Surgery was performed in 94.7% (n = 72), including hemithyroidectomy (n = 8), total thyroidectomy (TT) (n = 20) - 7 with two-staged surgeries, TT with bilateral recurrent dissection (n = 29), and TT with bilateral recurrent + lateral neck dissection (n = 15). The median tumour size was 14 mm, with 25 of 67 patients (37.3%) presenting microcarcinomas. R0 resection was achieved in 52 of 62 patients (83.9%). Vascular invasion was observed in 12 of 50 cases (24%), while extrathyroidal extension was observed in 12 of 63 cases (19%). Local cervical recurrence occurred in 18.8% (n = 13) (median time post-surgery: 6.5 months), treated surgically in 9 cases; the remaining patients were kept under surveillance. Additional therapy was performed in 13.2% of patients (n = 10): 9 had radiotherapy (cervical, n = 6; bone, n = 3), and 3 received tyrosine kinase inhibitors. Median follow-up was 67.5 months (IQR 24.8 – 121). At the most recent evaluation, 46.1% (n = 35) of patients were disease-free, 30.3% (n = 23) had biochemical evidence of disease, and 23.7% (n = 18) had structural disease (locoregional, n = 4; distant, n = 14 - bone (n = 7), liver (n = 5), lung (n = 8)). Among those with structural disease, 72.2% (n = 13) showed disease progression. A total of 21.1% of patients (n = 16) died, with 10 of these deaths attributed to MTC. Median overall survival was 66.5 months (IQR 25.5 – 119.3).

Conclusions: The importance of long-term follow-up is emphasized due to the possibility of recurrence or disease progression. Genetic testing is essential not only for individual prognosis but also for familial genetic counselling, in addition to enabling targeted systemic therapy when indicated.