Track: Clinical Studies

Abstract:

Sentinel lymph node biopsy (SLNB) remains the standard for staging melanoma, yet approximately 88% of patients undergoing SLNB have negative results. A study reported in the manufacturer’s evidence summary states that the i31-GEP has 100% sensitivity, 100% negative predictive value (NPV), 24.2% specificity, and 25.4% positive predictive value (PPV) for predicting SLNB positivity in T1–T4 melanomas. This study evaluates the real-world performance of i31-GEP over three years at a single institution. Patients aged 18 years or older with primary cutaneous melanoma (T1–T4) who underwent i31-GEP testing between January 2022 and December 2024 were included. Castle results were correlated with their SLNB results. Utilization increased annually, with 42, 45, and 77 tests performed in 2022, 2023, and 2024, respectively. The i31-GEP classified 99.2% of T1a, 100% of T1b, and 68.7% of T2a patients as low risk (<5% likelihood of SLNB positivity). For T1–T2 melanomas, 33 patients (84%) were classified as low risk and 6 (16%) as high risk (>10% likelihood of SLNB positivity), yielding a sensitivity of 100%, specificity of 86%, PPV of 16%, and NPV of 100%. For T1–T4 melanomas, 33 (70%) were low risk and 14 (30%) were high risk, yielding a sensitivity of 100%, specificity of 73%, PPV of 14%, and NPV of 100%. The i31-GEP may support personalized care, reduce morbidity, and lower costs by minimizing unnecessary SLNBs, but its limited stratification in very early-stage melanoma warrants further refinement. A limitation of this study is the small number of SLNB-positive cases in the cohort.

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Aadil Ahmed