Merlin_001: a prospective registry study of a primary melanoma gene-signature to predict sentinel node (SN) status and determine its prognostic value for more accurate staging of SN-negative melanoma patients

Abstract Background: Sentinel lymph node biopsy (SLNB) provides important staging and prognostic information that guides surveillance and adjuvant systemic therapy decisions for patients with cutaneous melanoma. At most centers, SLNB is indicated for patients with cutaneous melanoma with at least a 5% risk of having nodal metastases, typically melanomas ≥0.8 mm in thickness or selected thinner lesions with high-risk features such as elevated mitotic rate and/or ulceration. However, up to 85% of patients who undergo SLNB have a negative result. Currently, there is an unmet clinical need to better identify patients with a low risk of nodal metastasis who may safely forgo SLNB, but otherwise meet established criteria for undergoing SLNB. Previously, a model using primary tumor gene expression profile (GEP) data combined with clinicopathological features (CP) was developed to identify melanoma patients with a low risk of having a positive SLN. The model has been externally validated in multiple retrospective studies. The aim of the MERLIN_001 observational registry study is to prospectively validate the CP-GEP model in an independent multicenter cohort of primary cutaneous melanoma patients, who undergo lymphatic mapping and SLNB per current clinical guidelines. Methods: A total of 9 centers across the US are included in the study with planned enrollment of 2,340 patients, allowing for a loss of up to 30% due to screen failure, tissue loss, low RNA yield, no gene expression profile or failure to perform the planned SLNB. Patients with clinically node-negative cutaneous melanoma and planned SLNB using current guideline indications are eligible for the study and will be followed for five years. Both patients and investigators are blinded to the results (NCT04759781). FFPE material from the initial melanoma biopsy is collected and the GEP of the primary melanoma is assessed. Subsequently, CP-GEP probability scores are calculated and expressed as a binary classification (Low Risk or High Risk for nodal metastasis), which will be compared to SLNB pathology results. Performance metrics for CP-GEP will be evaluated and will include: SLNB Reduction Rate based on Negative Predictive Value, Positive Predictive Value, Sensitivity and Specificity, and the corresponding 95% confidence intervals. Finally, the performance of CP-GEP to stratify patients according to risk of recurrence (recurrence-free survival, distant metastasis-free survival, overall survival) will also be assessed, based on five-year outcomes data. Additional analyses will be performed using the data collected throughout the study. Enrollment of patients started in September 2021 and is ongoing. As of January 2023, 890 patients have been enrolled, representing 46% of the targeted number of patients with a successful SLNB and CP-GEP test result. Citation Format: Tina J. Hieken, Michael E. Egger, Christina V. Angeles, Erin E. Burke, Michael C. Lowe, John R. Hyngstrom, Georgia M. Beasley, Edmund K. Bartlett, Vernon K. Sondak. Merlin_001: a prospective registry study of a primary melanoma gene-signature to predict sentinel node (SN) status and determine its prognostic value for more accurate staging of SN-negative melanoma patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT053.