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Melanoma

E309: Utility of 31-gene expression profile test in identifying patients with T1 cutaneous melanoma at high risk of SLN positivity and recurrence

    Author(s)

  • SY

    Shawn Young, MD

    Physician
    Cancer Centers of Colorado (SCL Health), United States

  • HN

    Harrison Nguyen, MD, MBA, MPH

    Physician
    Perelman School of Medicine, University of Pennsylvania, United States

  • MT

    Michael Tassavor, MD

    Physician
    Mount Sinai Icahn School of Medicine, United States

    • Submitter(s)

  • BM

    Brian Martin, PhD

    Senior Scientist II
    Castle Biosciences, Inc.
    Friendswood, Texas, United States

    • Author(s)

  • BM

    Brian Martin, PhD

    Senior Scientist II
    Castle Biosciences, Inc.
    Friendswood, Texas, United States

  • PS

    Parth Shah, MD

    Physician
    Cancer Centers of Colorado (SCL Health), United States

    • ePoster Abstract Author(s)

  • BM

    Brian Martin, PhD

    Senior Scientist II
    Castle Biosciences, Inc.
    Friendswood, Texas, United States

Introduction:

Patients with thin ( < 1mm) (T1) cutaneous melanoma are generally not recommended for sentinel lymph node biopsy (SLNB) due to having a < 5% risk of a positive SLNB as per the NCCN guidelines (2023). However, some T1 tumors will still have a positive SLN and they contribute recurrences. The 31-Gene Expression Profile (31-GEP) test has been validated to identify patients with T1 tumors who can safely forego SLNB and in  stratifying patients according to their risk of recurrence.

Methods:

A pooled cohort of 979 patients (1998-2019) with T1 tumors was analyzed for SLN biopsy performance and SLNpositivity rates. Clinical data such as patient age, tumor location as well as pathology findings including the Breslow thickness, tumor ulceration, mitotic rate, transected base rate, regression, lymphovascular invasion, and TILS was collected and analyzed through multiple logistic regression analysis. Additional Kaplan-Meier analysis was performed to estimate a 5 year recurrence free survival (RFS).

Results:

In our cohort, 33.4% (327 patients) underwent SLN biopsy, of which 13.8% (45 patients) had positive SLN. Our analysis showed  the 31-GEP Class 1B/2A result (OR=2.60, 95% CI 1.10-5.98), a Class 2B result (OR=9.02, 95% CI 3.26-25.80), and tumor regression (OR=0.18, 95% CI 0.04-0.59) as the only factors associated with a risk fo positive SLN. Additionally, patients with a Class 2B result had numerically lower 5-year RFS rates than patients with a positive SLN biopsy (58.7% vs. 69.0%, p=0.354), while those with a Class 1A result had similar 5-year RFS rates as those of SLN negative patients (93.2% vs. 93.6%, p=0.662). Patients with a Class 2B and a positive SLN had a 50.8% 5-year RFS. A positive SLN (HR=4.76, 95% CI 1.98-11.3) and a Class 2B result (HR=4.40, 95% CI 1.65-11.4) were significant predictors of recurrence.

Conclusions:

In patients with T1 cutaneous melanoma undergoing SLN biopsy, the 31-GEP strongly predicted SLN positivity and it may provide prognostic information similar to SLN biopsy.

Learning Objectives:

  • Upon completion, participant will be able to discuss the utility of 31-GEP testing for SLNB guidance.
  • Upon completion, participant will be able to discuss the utility of 31-GEP testing in risk of recurrence prediction.
  • Upon completion, participant will understand the role of 31-GEP testing in patients with T1 tumors.