Effect of Sentinel Lymph Node Biopsy and LVI on Merkel Cell Carcinoma Prognosis and Treatment

Objective: Prognostic factors and optimal treatment approaches for Merkel cell carcinoma (MCC) remain uncertain. This study evaluated the influences of sentinel lymph node (SLN) biopsy and lymphovascular invasion (LVI) on treatment planning and prognosis. Study Design: Retrospective cohort study. Methods: Stage 1 to 3 MCC patients treated 2005 to 2018. Predictors of nodal radiation were tested using logistic regression. Predictors of recurrence-free, disease-specific, and overall survival were tested in Cox proportional hazard models. Results: Of 122 patients, 99 were without clinically apparent nodal metastases. Of these, 76 (77%) underwent excision and SLN biopsy; 29% had metastasis in SLNs, including 20% of MCCs 1 cm or less. Primary tumor diameter, site, patient age, gender, and immunosuppressed status were not significantly associated with an involved SLN. Among patients who underwent SLN biopsy, 13 of 21 (62%) MCCs with LVI had cancer in SLNs compared with 14 of 44 (25.5%) without LVI (P =.003). Although local radiation was common, nodal radiation was infrequently employed in SLN negative (pathologic N0) patients (21.8% vs. 76.2% for patients with SLN metastases, P =.0001). Survival of patients with positive SLNs was unfavorable, regardless of completion lymphadenectomy and/or adjuvant radiation. After accounting for tumor (T) and node (N) classification, age, immunosuppression, and primary site, a positive SLN and LVI were independently associated with worse survival (LVI/recurrence-free survival [RFS]: hazard ratio [HR] 2.3 (1.04–5, P =.04; LVI/disease-specific survival [DSS]: HR 5.2 (1.8–15, P =.007); N1a vs. pN0/RFS HR 3.6 (1.42–9.3, P =.007); DSS HR5.0 (1.3–19, P =.17). Conclusion: SLN biopsy assists in risk stratification and radiation treatment planning in MCC. LVI and disease in SLNs, independently associated with worse survival, constitute markers of high-risk disease warranting consideration for investigational studies. Level of Evidence: III Laryngoscope, 131:E828–E835, 2021.