Cytopathology and Prognostic Accuracy of 15-GEP/PRAME

Importance: Gene expression profiling (GEP) reliably predicts metastatic uveal melanoma risk and is used to manage uveal melanoma (UM) in patients with this diagnosis. Efforts to refine molecular prognostication continue. Objective: To determine if confirmatory cytopathology findings influence the prognostic accuracy of a commercially available GEP/Preferentially Expressed Antigen in Melanoma (PRAME) assay. Design, Setting, and Participants: The Collaborative Ocular Oncology Group 2 study, a prospective cohort study, was conducted from 2017 to 2020 with follow-up recorded at 6-month intervals. This was a multicenter study that included patients with choroidal and/or ciliary body melanoma and results from a 15-GEP and PRAME RNA expression (15-GEP/PRAME) assay. Patients with iris tumors or less than 6 months' follow-up were excluded. Study data were analyzed from April 2025 to July 2026. Exposures: 15-GEP/PRAME, cytopathology, and next-generation sequencing (NGS). Main Outcomes and Measures: Metastatic uveal melanoma rates in patients who had 15-GEP/PRAME and confirmatory cytopathology (CCP) results confirming or suspicious for UM (GEP+CCP) were compared with those who had 15-GEP/PRAME and no cytopathology performed, or unknown or nondiagnostic cytopathology results (GEP only). UM-associated variants identified by NGS were also evaluated. Results: Of 1537 patients (mean [SD] age, 62.0 [13.4] years; 787 male [51.2%]), 727 (47.3%) had CCP results, and 810 (52.7%) had nondiagnostic cytopathology results or no cytopathology performed. Class 2/PRAME+ tumors were more common (136 of 727 [18.7%]) in the GEP+CCP group than in the GEP-only group (72 of 810 [8.9%]; 9.8% difference; 95% CI, 6.4-13.3; P <.001), whereas class 1/PRAME- tumors were less common (330 of 727 [45.4%] vs 495 of 810 [61.1%]; 15.7% difference; 95% CI, 10.8-20.6; P <.001). In patients with GEP+CCP, 22.7% (n = 165) developed metastasis vs 15.4% (n = 125) in patients with GEP only (7.3% difference, 95% CI, 3.3-11.2; P < .001). Adjusting for 15-GEP/PRAME status, there were no differences in metastasis rates between CCP groups. Of 1327 patients with successful NGS, 94.1% (605 of 643) in the GEP+CCP group and 71.9% (492 of 684) in the GEP-only group had a UM-associated variant (22.2% difference, 95% CI, 18.3-26.0; P < .001). Conclusions and Relevance: Results of this cohort study reveal that no differences in metastasis outcomes were observed between patients with and without CCP within any GEP/PRAME categories. UM-associated variants were found less frequently in the GEP-only group than in the GEP+CCP group. In this cohort, 15-GEP/PRAME classification without CCP retained prognostic validity, supporting its clinical consideration in guiding metastatic surveillance in cases in which cytopathology is unavailable.