Improved Staging of Ciliary Body and Choroidal Melanomas Based on Estimation of Tumor Volume and Competing Risk Analyses

The current, 8th edition of the American Joint Committee on Cancer (AJCC) anatomic classification and staging model for uveal melanoma does not fully separate survival estimates for patients with advanced stages of the disease (e.g., IIIB and IIIC). Furthermore, some tumors in higher size categories have a smaller volume than tumors in lower categories. Therefore, we developed a novel model for prognostication of metastatic mortality based on estimations of tumor volume. Retrospective, multicenter case series of patients with uveal melanoma involving the choroid, ciliary body, or both. Six thousand five hundred twenty-eight consecutively registered patients treated at 3 tertiary ocular oncology centers on 2 continents between 1981 and 2022. Data on survival, tumor size, and extent were collected for all 6528 patients. Tumor volume was estimated using a simple equation based on largest basal diameter and thickness. Volume-based size categories and stages were developed and validated in independent patient cohorts using competing risk analyses, and correlations with cytogenetic and cytomorphologic features were examined. Cumulative incidence of metastatic death. The 6528 patients were distributed over 7 stages based on estimated tumor volume and anatomic extent (V stages IA, IB, IIA, IIB, IIIA, IIIB, and IIIC), with a 15-year incidence of metastatic death ranging from 7% to 77%. A new category, V1 min, and corresponding stage IA, were introduced, indicating an excellent prognosis. Metastatic mortality in V stage IIIC was significantly higher than that in V stage IIIB ( P  = 0.03), whereas incidence curves crossed for patients in AJCC stages IIIC vs. IIIB ( P  = 0.53). Univariable and multivariable competing risk regressions demonstrated higher Wald statistics for V stages compared with AJCC stages (1152 vs. 1038 and 71 vs. 17, respectively). The frequency of monosomy 3, gain of chromosome 8q, and epithelioid cytomorphologic features increased with tumor volume ( R 2  = 0.70, R 2  = 0.50, and R 2  = 0.71, respectively; P < 0.001) and showed similar correlations with both AJCC and V stages. Anatomic classification and staging of ciliary body and choroidal melanomas based on estimation of tumor volume improves prognostication of metastatic mortality. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.