The 31-GEP to identify patients with localized cutaneous melanoma at the highest risk of metastasis to the central nervous system.

Abstract

9530 Background: Cutaneous melanoma (CM) metastasis to the central nervous system (CNS) has a poor prognosis; however, treatment of CNS metastasis while asymptomatic is associated with better outcomes. CNS imaging is not routinely recommended for patients with early-stage CM (i.e., AJCC stage I–II), yet ˜14% of patients with stage II melanoma will develop CNS metastases. The 31-gene expression profile test (31-GEP) identifies patients at a low (Class 1A), intermediate (Class 1B/2A), or high risk (Class 2B) of tumor recurrence and metastasis. We evaluated the association of CNS metastasis with the 31-GEP test result for the purpose of directing CNS-directed imaging to detect metastasis earlier and, thus, improve outcomes. Methods: A retrospective analysis of patients clinically tested with the 31-GEP from 2013-2017. Patients were included in the study if they had clinical or pathological AJCC stage I-II CM (n=1,662). Kaplan-Meier analysis was used to estimate 5-year recurrence-free survival (RFS), and the log-rank test was used to compare survival between groups. Patients with non-CNS metastasis were censored at the time of recurrence. Univariate analysis to identify predictors of CNS metastasis was performed for tumor location, mitotic rate, Breslow thickness, ulceration status, tumor-infiltrating lymphocytes, age, sex, regression, lymphovascular invasion, tumor subtype, and 31-GEP results. Only significant (p<0.01) factors in univariate analysis were included in Cox multivariable analysis. Results: Median follow-up time was 4.6 years (range: 0.02-14.5 years). Patients with a CNS metastasis tended to have thicker tumors (median 1.1 vs. 0.8, p=0.003), higher mitotic rate/mm2 (median 2.5 vs. 1.0, p<0.001) and a higher proportion of males (73% vs. 55%, p=0.03) than patients that did not develop CNS metastasis. Patients with a Class 2B result were significantly more likely to develop CNS metastasis (7.4% [15/202]) relative to patients with a Class 1B/2A (1.7% [5/291]) or Class 1A (0.9% [10/1,169], p<0.001) 31-GEP result. Patients with a Class 2B result had significantly lower 5-year RFS than patients with a Class 1B/2A or Class 1A result (91.6% vs. 98.2% vs. 99.1%, p<0.001) and had shorter times to CNS metastases (1.5 yrs. vs. 4.2 yrs. vs. 3.4 yrs. p<0.001). In multivariable analysis, only the 31-GEP Class 2B (HR=9.42, p<0.001) result was a significant predictor of CNS metastasis; mitotic rate, Breslow thickness, and ulceration were not significantly predictive. Conclusions: Under multivariable analysis, the 31-GEP was the only significant predictor of CNS metastasis, and CNS metastasis occurred early (1.5 yrs). Patients with early-stage I-II CM and a Class 2B result should be considered for CNS imaging to enable asymptomatic detection of CNS metastasis and, thus, improve survival relative to symptomatic CNS metastasis.