Medullary Thyroid Cancer: Single Institute Experience over Three Decades and Risk Factors for Recurrence.

CONTEXT:Medullary thyroid cancer has a historic recurrence rate up to 50%, and surgery remains the only cure. OBJECTIVE:This study aims to assess factors related to recurrence and metastatic spread in MTC. DESIGN:Retrospective chart review was performed from 1990-2023. Descriptive analysis and regression models were used for analysis. SETTING:Single specialized tertiary care referral center. PATIENTS:68 patients with MTC, who underwent surgery, were included. MAIN OUTCOME MEASURE:Recurrence. RESULTS:Mean age at diagnosis was 54.9years(42.2-64.1), 65%(n=44) females. Lymph node and distant metastases were found in 24%(n=16) and 4%(n=3), respectively. RET mutations were present in 52%(n=35): MTC risk levels Highest 6%, High 7%, and Moderate 39%. Mean tumor size was 1.9cm(1.2-3.2) and mean preoperative calcitonin was 504.4pg/mL(133.2-1833.8). Total thyroidectomy(TT) was performed in 10 patients, TT+central neck dissection(CND) in 28, and TT+CND+lateral neck dissection(LND) in 25. On final pathology, 40% had positive central nodes and 25% had positive lateral nodes. Recurrence was 22%, median follow-up 4.7years(1.2-28.0). Male gender(HR=5.81, p=0.021), positive lateral neck nodes(HR 8.10, p=0.011) and high/highest MTC risk level RET mutations(HR 8.66, p=0.004) were significantly associated with recurrence. Preoperative calcitonin>2,175 pg/mL was a strong predictor for distant metastasis(AUC0.893) and a good predictor for lateral neck disease(AUC0.706). Extent of surgery was not significantly associated with recurrence(p=0.634). CONCLUSION:One of 4 patients undergoing surgery for MTC will recur. Risk factors associated with recurrence are male gender, lateral LN metastasis and high/highest MTC risk level mutations, but not necessarily surgery type. Preoperative calcitonin>2,175 pg/mL is suggestive of advanced disease and should prompt further evaluation.