Oncologic Outcome of Bimodality Approach for Cutaneous Adnexal Carcinoma

Abstract

Purpose/Objective(s): Merkel cell carcinoma (MCC) is a rare neuroendocrine malignancy of the skin with a predilection for aggressive behavior. Previous studies evaluating sentinel lymph node biopsy (SLNB) in MCC have shown positivity rates typically ranging from 22% to 48% in clinically N0 patients. The benefit of SLNB has also been well established in other similarly aggressive tumors, such as melanoma. As a result, sentinel lymph node biopsy (SLNB) is currently recommended for all clinically N0 patients, though its impact remains unclear. The aim of this review was to evaluate for a survival benefit in clinically N0 patients undergoing SLNB. Materials/Methods: The Surveillance, Epidemiology, and End Results (SEER) database was used to identify patients diagnosed with MCC from 2003 through 2012 with skin as the primary site. Patients up to age 75 years were included, provided they underwent a cancer-directed surgery. Patients with positive lymph nodes or distant disease were excluded. Cause-specific survival was then compared in patients who underwent SLNB as opposed to no pathologic nodal evaluation. Results: A total of 603 patients were identified who met the above criteria. Patients undergoing SLNB had a median age of 65 years with a range of 38-75, 59% were male, and 95% were white. With regard to tumor size: 57% were 2 cm, 13% were 2-5 cm, and 30% were >5 cm. In all, 52% of patients received radiation. Patients with no pathologic nodal evaluation had a median age of 68 years with a range of 37-75, 60% were male, and 94% were white. With regard to tumor size, 34% were 2 cm, 19% were 2-5 cm, and 47% were >5 cm. A total of 48% of patients received radiation. Patients undergoing SLNB had an improved 5-year CSS of 91.3% (95% CI 86.4-94.5%) compared to the nonpathologic nodal evaluation group, with a 5-year CSS of 72.5% (95% CI 65.4-78.4%). When analyzing tumors 2cm, the improved outcome was maintained for SLNB patients vs nonpathologic the nodal evaluation group with a 5-year CSS of 94.70% (95% CI 88.4-97.6) compared to 79.3% (95% CI 66.6-87.6%). Conclusion: A CSS advantage was found for patients undergoing SLNB. This advantage remained significant when stratifying for tumors <2 cm. The reason for this advantage is not fully clear but could be in part from decreased false negatives for nodal staging, therapeutic effect of the SLNB, or a result of more complete care. While prospective data are needed to confirm these findings, the rare nature of these tumors renders this a clinical challenge. Regardless, our current findings support the standard of care of SLNB in clinically N0 patients.