Purpose To validate a staging system for metastatic uveal melanoma that will facilitate planning, reporting, and interpreting the results of clinical trials. Design Reliability and validity study. Methods The performance index, the largest diameter of the largest metastasis and alkaline phosphatase level at the time of diagnosis of metastases, and overall survival of 249 patients from 7 ocular oncology centers who died of dissemination were analyzed. Predicted median survival time calculated according to the Helsinki University Hospital Working Formulation was used to assign patients to stages IVa, IVb, and IVc, which correspond to predicted survival times of ≥12, <12-6, and <6 months, respectively. The predictions were compared against observed survival. Results The 3 variables used to assign stage were independent predictors of survival in the validation dataset. Of the 249 patients, 110 (44%), 109 (44%), and 30 (12%) were classified to Working Formulation stages IVa, IVb, and IVc, respectively. Corresponding median observed survival times were 18.6, 10.7, and 4.6 months and worsened by increasing stage (P < .001). Of 201 patients managed without surgical resection of metastases, 83 (41%), 89 (44%), and 29 (15%) were classified to stages IVa, IVb, and IVc, respectively, and their median observed survival times were 17.2, 10.0, and 4.6 months (P < .001). Survival of 47 patients who underwent resection did not differ by working formulation stage (P = .69). Conclusions This multicenter study confirms that the Working Formulation is a reliable and valid, repeatable system for dividing metastatic uveal melanoma into distinct prognostic subgroups, especially for stage-specific reporting of survival in prospective clinical trials.
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