Medullary Thyroid Carcinoma Detected by Routine Health Screening Had Better Clinical Outcome and Survival

Background: The benefits of early detection in medullary thyroid carcinoma (MTC) are not well established. This study investigates the impact of early detection of MTC on clinical outcomes. Methods: This retrospective study evaluated 144 patients diagnosed with MTC at Samsung Medical Center between 1995 and 2019, classified as asymptomatic (mostly detected through routine health check-ups, including ultrasonography, calcitonin, or carcinoembryonic antigen levels) and symptomatic. Initial treatment response, final clinical outcomes, and cancer-specific survival were compared. Results: MTC was diagnosed in 104 (72.2%) asymptomatic and 40 (27.8%) symptomatic patients. The symptomatic group showed a significantly larger primary tumor size, more frequent lateral neck lymph node metastasis, more advanced tumor, node, metastasis (TNM) staging, and higher pre-and postoperative serum calcitonin levels. For initial treatment response, the proportion of excellent responders was significantly higher in the asymptomatic group (71.2% vs. 40.0%), while that of patients with biochemical incomplete response (37.5% vs. 26.9%) and structural incomplete response (22.5% vs. 1.9%) was significantly higher in the symptomatic group (all P<0.001). For the final clinical outcomes, the rate of patients with no evidence of disease was higher in the asymptomatic group (67.3% vs. 30.0%), while the rate of patients with structurally identifiable disease was higher in the symptomatic group (45.0% vs. 7.7%) (P<0.001 for both). The symptomatic group had significantly poorer cancer-specific survival than the asymptomatic group (log-rank P=0.023). Conclusion: Compared with late diagnosis through symptomatic presentation, early diagnosis in asymptomatic patients results in significantly better initial treatment response, final clinical outcomes, and cancer-specific survival in patients with MTC.