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Presentation

Gene Expression Profiling for Diagnosis and Prognosis in Melanoma

Description

The presentation discusses commercially available genetic tests for melanoma, focusing on gene expression profiling (GEP) tests that assist in diagnosis and prognosis. It differentiates between germline and somatic testing, stressing the importance of the 23 gene expression test (MyPath) for ambiguous melanocytic lesions, which boasts a high sensitivity of approximately 91%. However, the test has limitations, including a significant indeterminate rate and the exclusion of metastatic lesions in original studies. Subsequent studies have shown variable performance, suggesting the need for further validation. Additionally, the call for a second test, the 35 gene expression profiling test (DIF DX), is noted to address some weaknesses of the original test. The tape stripping test, designed to discern the necessity of biopsies based on RNA expression from the skin, is also discussed, with specific anatomical limitations. Prognostically, the 31 gene expression profiling test categorizes melanoma into low or high metastatic risk; however, its predictive capabilities regarding disease progression have raised concerns about clinical utility. Recent studies among melanoma experts indicate a reluctance to incorporate these tests into routine practice due to insufficient evidence supporting their impact on treatment decisions. Lastly, a local coverage determination by CMS has deemed some GEP tests not medically necessary, highlighting ongoing debates in the field regarding their effectiveness and validation.

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Conclusions

The 23-gene expression profiling test has a sensitivity of approximately 91% and specificity also around 91%.
This test aids in differentiating between malignant melanomas and benign melanocytic lesions.
The performance of the test remains consistent across various cohorts, although some real-world applications show reduced sensitivity and specificity compared to initial studies.
An indeterminate score option now exists for cases that do not fit definitively into benign or malignant categories, reflecting the test's limitations.
About 23% of cases may yield no results, and there is a significant rate for indeterminate results in both unequivocal and ambiguous cases.
The introduction of a 35-gene expression profiling test (DiffDx) aims to improve diagnosis in challenging cases like melanoma in situ.
Tape stripping assays can help guide biopsy decisions by classifying risk levels associated with pigmented lesions, although they are limited to non-invasive sites.
The PRAME immunohistochemistry test shows potential correlations with the 23-gene signature test, suggesting it might serve as a reasonable surrogate in some cases.
Gene expression profiling results were shown to support histopathological diagnoses in a significant majority of cases, thus enhancing clinical decision-making processes without compromising specificity.
Overall, the use of these tests is not yet widely accepted for routine clinical decision-making due to the need for further validation and potential changes in management plans.

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