Clinical Outcomes of 160 Patients with Clinically Node-Negative Merkel Cell Carcinoma after Wide Excision and Sentinel Lymph Node Biopsy

Abstract

INTRODUCTION: Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer with high nodal metastasis rates. Studies regarding the prognostic significance of sentinel lymph node (SLN) status differ. We evaluated the outcomes of MCC patients after wide excision + sentinel lymph node biopsy (WE+SLNB). METHODS: A retrospective review of 160 MCC patients who underwent WE+SLNB at our institution (April 2005 through July 2021) was performed. Clinicopathologic variables and outcomes were assessed. RESULTS: Sixty-four patients (40%) were SLNB(+), 92 (58%) were SLNB(–); 4 did not map. SLNB(+) patients were more likely to be female (42% vs 27%, p = 0.05), have larger primary tumors (13.0 vs 7.4 mm, p < 0.001), higher rates of lymphovascular invasion (61% vs 36%, p = 0.006), and infiltrative growth patterns (72% vs 62%, p = 0.048). Most SLNB(+) patients received further nodal therapy: completion lymph node dissection (CLND, n = 9), CLND with radiotherapy (n = 6), or radiotherapy (n = 26). Patients who underwent CLND (n = 15, 23%) were more likely to have SLNs with extracapsular extension (40% vs 14%, p = 0.02) and receive systemic therapy (80% vs 51%, p = 0.07), and less likely to receive nodal basin radiotherapy (40% vs 71%, p = 0.04) than those who did not undergo CLND. At a median follow-up of 32 months, 40% of SLNB(–) patients recurred vs 48% of SLNB(+) patients (with CLND, 67%; without CLND, 43%; Table). Recurrence-free survival for SLNB(–), SLNB(+) without CLND, and SLNB(+) with CLND patients was 61.6, 35.6, and 26.8 months, respectively. Table. - Outcomes of MCC Patients Who Underwent WE+SLNB Outcomes Total cohort (n = 160) (+) SLNB (n = 64) (–) SLNB (n = 92) With CLND (n=15) Without CLND (n=49) Overall survival, mo, median (range) 89 (1–199) 35 (0–40) 69 (0–69) 105 (0–199) Recurrence-free survival, mo, median (range) 39 (25–69) 27 (13–39) 36 (20–69) 62 (19–X) Any recurrence, N (%) 69 (43) 10 (67) 21 (43) 37 (40) Status at last follow-up, N (%) Alive, no evidence of disease 94 (58.9) 5 (33.3) 28 (57.1) 56 (63.0) Alive with disease 16 (10.0) 3 (20.0) 5 (10.2) 8 (8.7) Deceased 50 (31.3) 7 (46.7) 16 (32.7) 26 (28.3) CONCLUSION: SLNB(–) patients had better outcomes than SLNB(+) patients. Among the SLNB(+) patients, CLND was associated with worse outcomes. Work to evaluate trends in the multimodal treatment of SLNB(+) MCC patients and the impact on outcomes is underway.