Enabling Access to Prognostic Gene Expression Profile (GEP) Testing for Invasive Melanoma by Leveraging RNA-based Testing in the Diagnostic Workflow

Background: 31-GEP prognostic testing is an important tool for patients diagnosed with invasive melanoma and stratifies patients into groups at low, intermediate, or high risk of recurrence, metastasis, or death. The pathway to a melanoma diagnosis is not always straightforward and often dermatopathologists utilize molecular testing to assist in the accurate classification of ambiguous lesions, which utilize varied tissue amounts. Separately, the 23-GEP test is an objective molecular ancillary diagnostic test which uses RNA extracted from 9 unstained slides. Both diagnostic (23-GEP) and prognostic (31-GEP) tests are offered from the same laboratory and can utilize the same RNA. Here, 23-GEP clinical order trends are described March through July 2023. Methods: 23-GEP orders from March through July 2023 were analyzed. Results: 23-GEP tissue was primarily obtained from shave biopsies (88.6%, where biopsy type was specified). 57.5% of samples were female and median patient age was 49.5 years old. The test result distribution was 61.8% benign, 20.3% malignant, 13.7% intermediate, and 4.2% technical fail. Median turnaround time (TAT) (calculated as receipt of tissue until report date and inclusive of weekends and holidays) of 23-GEP was 4 days (interquartile range = 2, 5). If a 23-GEP-tested clinical order subsequently receives an invasive melanoma diagnosis, 31-GEP can be utilized efficiently without additional tissue and RNA extraction time. Conclusions: Overall, when the 23-GEP ancillary test is utilized to achieve a confident diagnosis in an otherwise ambiguous neoplasm, rapid access to 31-GEP prognostication without the need for additional tissue can be achieved.