Cytogenetic Abnormalities for Predicting the Risk of Metastases in Choroidal and Ciliary Body Melanoma

PURPOSE. Choroidal melanoma (CM) and ciliary body melanoma (CBM) are the two most common subtypes of uveal melanoma. Starting from the observation that CBM tends to have a higher metastatic potential than CM, we hypothesized that specific cytogenetic abnormalities could be associated with tumor location – reflecting distinct genetic signatures that would drive the risk of distant spread. METHODS. Chromosomal alterations were investigated by molecular cytogenetic techniques in 217 and 97 patients with CM and CBM, respectively. Cox proportional hazards regression analysis was used to identify the independent predictors of distant metastasis. RESULTS. Patients with CBM had larger tumor sizes (P < 0.001), higher disease stages (P < 0.001), and more frequently showed distant metastasis (P = 0.002) than those with CM. On analyzing the entire study cohort, we found that specific chromosomal alterations – including chromosome 8p loss (P < 0.001), 1p loss (P < 0.001), and monosomy 3 (P < 0.005) – were independent predictors of distant metastasis. Based on a decision-tree learning algorithm, we identified three specific subgroups of patients with uveal melanoma at high risk of distant spread. Monosomy 3 occurred significantly more frequently in patients with T3 CBM tumors. CONCLUSIONS. Specific cytogenetic abnormalities – including chromosome 8p loss, 1p loss, and monosomy 3 – are independent risk factors for distant metastasis in uveal melanoma. Larger tumor size at presentation and monosomy 3 contribute to a higher metastatic risk in patients with CBM.