The Effect of Extent of Surgery and Number of Lymph Node Metastases on Overall Survival in Patients with Medullary Thyroid Cancer

Context: Total thyroidectomy with central lymph node dissection is recommended in patients with medullary thyroid cancer (MTC). However, the relationship between disease severity and extent of resection on overall survival remains unknown. Objective: The aim of the study was to identify the effect of surgery on overall survival in MTC patients. Methods: Using data from 2968 patients with MTC diagnosed between 1998 and 2005 from the National Cancer Database, we determined the relationship between the number of cervical lymph node metastases, tumor size, distant metastases, and extent of surgery on overall survival in patients with MTC. Results: Older patient age (5.69 [95% CI, 3.34-9.72]), larger tumor size (2.89 [95% CI, 2.14-3.90]), presence of distant metastases (5.68[95% CI, 4.61-6.99]), and number of positive regional lymph nodes (for >= 16 lymph nodes, 3.40 [95% CI, 2.41-4.79]) were independently associated with decreased survival. Overall survival rate for patients with cervical lymph nodes resected and negative, cervical lymph nodes not resected, and 1-5, 6-10, 11-16, and >= 16 cervical lymph node metastases was 90, 76, 74, 61, 69, and 55%, respectively. There was no difference in survival based on surgical intervention in patients with tumor size <= 2 cm without distant metastases. In patients with tumor size > 2.0 cm and no distant metastases, all surgical treatments resulted in a significant improvement in survival compared to no surgery (P < .001). In patients with distant metastases, only total thyroidectomy with regional lymph node resection resulted in a significant improvement in survival (P < .001). Conclusions: The number of lymph node metastases should be incorporated into MTC staging. The extent of surgery in patients with MTC should be tailored to tumor size and distant metastases.