Medullary Thyroid Cancer: Single Institute Experience Over 3 Decades and Risk Factors for Recurrence.

Context: Medullary thyroid cancer (MTC) 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.

Methods: Retrospective chart review was performed from 1990 to 2023 at a single specialized tertiary care referral center. Descriptive analysis and regression models were used for analysis. Sixty-eight patients with MTC, who underwent surgery, were included and the main outcome measure was recurrence.

Results: Mean age at diagnosis was 54.9 years (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 were highest 6%, high 7%, and moderate 39%. Mean tumor size was 1.9 cm (1.2-3.2) and mean preoperative calcitonin was 504.4 pg/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 4.7 years (1.2-28.0). Male gender (hazard ratio [HR] 5.81, P = .021), positive lateral neck nodes (HR 8.10, P = .011), and high/highest MTC risk level RET mutations (HR 8.66, P = .004) were significantly associated with recurrence. Preoperative calcitonin >2175 pg/mL was a strong predictor for distant metastasis (area under the curve [AUC] 0.893) and a good predictor for lateral neck disease (AUC 0.706). Extent of surgery was not significantly associated with recurrence (P = .634).

Conclusion: One of 4 patients undergoing surgery for MTC will recur. Risk factors associated with recurrence are male gender, lateral lymph node metastasis, and high/highest MTC risk level mutations, but not necessarily surgery type. Preoperative calcitonin >2175 pg/mL is suggestive of advanced disease and should prompt further evaluation.