Introduction: Long-term outcomes after curative resection in patients with germline RET mutations and medullary thyroid cancer (MTC) are highly variable and mutation-specific oncologic outcomes are not well-described.
Methods: Sixty-six patients identified from 1986 to 2017 from a single-institution cancer database were assessed for recurrence and survival using Kaplan-Meier estimates, and correlated with clinicopathologic features using log-rank or Cox proportional hazards.
Results: Median follow-up was 9.3 years (range 0.3-31.5), median tumor diameter was 1.5 cm (range 0.1-7.5), and preoperative calcitonin was known in 41 patients [median 636 (range 0-9600)]. Overall survival (OS) of the cohort was 94% at 10 years, the cumulative incidence of locoregional recurrence was 38% at 10 years, and 19/24 (79%) patients underwent repeat neck operation. The cumulative incidence of distant recurrence was 27% at 10 years. Predictors of distant recurrence were tumor size, positive lymph nodes, and pre- and postoperative carcinoembryonic antigen, but not calcitonin. M918T mutation-bearing patients had 10-year distant recurrence-free survival of 0%, compared with 83% in all other patients (p < 0.001), and equivalent 10-year OS (100% vs. 92%; p = 0.49).
Conclusions: Structural and metastatic recurrence is common in patients with germline RET mutations, and MTC and can occur 20 years after initial treatment, however survival remains high. Management should focus on optimal surveillance strategies and long-term control of structural disease.