Comparing Two Gene Expression Profile Tests to Standard of Care for Identifying Patients With Cutaneous Melanoma at Low Risk of Sentinel Lymph Node Positivity.

Background/Aim: The National Comprehensive Cancer Network (NCCN) Guidelines for cutaneous melanoma (CM) recommend avoiding sentinel lymph node biopsy (SLNB) when the positivity risk is <5%, considering SLNB when the risk is 5-10%, or offering SLNB when the risk is >10%. Most patients undergoing SLNB have a negative result, showing that reliance upon the American Joint Committee on Cancer (AJCC) T-stage alone results in most patients undergoing an unnecessary, negative, unreliable, invasive procedure. Materials and Methods: Two gene expression profile (GEP) tests, the CP-GEP and the 31-GEP, have been developed to identify patients at low risk of SLN positivity who may consider avoiding SLNB. We analyzed the accuracy of the CP-GEP and 31-GEP in identifying patients with <5% risk of SLN positivity across the five validation studies of the CP-GEP and four validation studies of the 31-GEP in T1-T2 tumors. Results: Patients considered low risk by the CP-GEP had an SLN positivity rate of 6.2%, higher than the risk threshold of 5% used by the NCCN to guide SLNB decisions. In contrast, patients considered low risk by the 31-GEP or i31-SLNB had a 2.8% SLN positivity rate, a substantial improvement over AJCC-staging guidance. Conclusion: Overall, the CP-GEP did not perform as well as AJCC, while the 31-GEP performed better than AJCC.