Online risk calculator and nomogram for predicting sentinel lymph node positivity in Merkel cell carcinoma

Merkelcell.org Summary

Patients diagnosed with Merkel cell carcinoma often undergo a sentinel lymph node biopsy (SLNB) to guide treatment decisions. Compared to melanoma, MCC has a higher chance of positive sentinel lymph node biopsy (always >10%) and is indicated in most patients. However, a recent study found that only ~50% of MCC patients actually undergo sentinel lymph node biopsy. As summarized in this highlighted study, Maloney and co-authors have now developed an online calculator that predicts the risk of sentinel lymph node metastasis in MCC patients by using factors that include primary site, presence of lymphovascular invasion (LVI), tumor size, and immunosuppression. This tool reinforces the importance of patients undergoing sentinel lymph node biopsy for MCC and can also help guide treatment decisions in cases where SLNB is inconclusive or not feasible.

Abstract

National Comprehensive Cancer Network guidelines recommend that localized, clinically node-negative Merkel cell carcinoma (MCC) be treated with surgery to the primary tumor ± adjuvant radiation therapy, along with sentinel lymph node biopsy (SLNB). A recent investigation suggested rates of lymph node evaluation in MCC have plateaued at ∼50% of cases where it is indicated. Lack of nodal evaluation delays staging and further management with radiation or lymph node dissection. In the setting of nondiagnostic or potential false-negative sentinel lymph node biopsies, the yield of adjuvant treatment to the nodal basin is unclear. Prior studies have not investigated precisely how the risk of sentinel lymph node positivity is influenced by pathologic features. To further explore this topic, we investigated features associated with a positive SLNB and created a nomogram to estimate the risk of sentinel lymph node metastasis, which could help guide decisions regarding adjuvant treatment in the setting of a nondiagnostic SLNB.