Sentinel Lymph Node Biopsy is Associated with Improved Survival in Merkel Cell Carcinoma

Although sentinel lymph node biopsy (SNB) has become a standard for Merkel cell carcinoma (MCC), the impact on survival is unclear. To better define the staging and therapeutic value of SNB, we compared SNB with nodal observation. Patients with clinical stage I and II MCC in the Surveillance, Epidemiology, and End Results (SEER) registry undergoing surgery between 2003 and 2009 were identified and divided into two groups-SNB and observation. A total of 1,193 patients met the inclusion criteria (SNB 474 and Observation 719). The median age was 78 years, and the majority were White (95.3 %), male (58.8 %), received radiation therapy (52.9 %) and had T1 tumors (65.3 %). Twenty-four percent had a positive SNB. SNB patients were younger (73 vs. 81 years; p < 0.0001), had T1 tumors (69.6 vs. 62.5 %; p = 0.04) and received radiotherapy (57.8 vs. 40 %; p < 0.0001). Among biopsy patients, a negative SNB was associated with improved 5-year MCC-specific survival (84.5 vs. 64.6 %; p < 0.0001). Univariate analysis demonstrated an increased 5-year MCC-specific survival for the SNB group versus the Observation group (79.2 vs. 73.8 %; p = 0.004), female gender (83.2 vs. 70.4 %; p = 0.0004), and lower T stage (p < 0.0001). On Cox regression, diminished survival was noted for the Observation group (risk ratio [RR] 1.43; p = 0.04), male gender (RR 2.06; p < 0.0001), and a higher T stage. SNB for MCC provides prognostic information and is associated with a significant survival advantage.