Cause-specific mortality coding: Methods in the Collaborative Ocular Melanoma Study COMS Report No. 14

Ascertainment of cause of death is often sought in clinical trials in which mortality is an outcome of interest. Standardized methods of coding all-cause and disease-specific mortality were developed and evaluated in the Collaborative Ocular Melanoma Study randomized trial of pre-enucleation radiation of large choroidal melanoma. All available clinical and pathologic materials documenting events prior to each reported death were reviewed systematically by a Mortality Coding Committee (MCC) to determine whether melanoma metastasis or local recurrence was present at the time of death. A level of certainty was assigned based on availability of local or central review of pathology materials. The outcome of the mortality coding protocol was evaluated both by assessing agreement between the judgment of the MCC and the presumed cause of death reported by the clinical center and, for a subset of patients, by assessing agreement between the MCC classification and the cause of death reported on the death certificate. As of July 31, 1997 (the cutoff date for the initial mortality report), 435 (95%) of 457 deceased patient files had been reviewed. The MCC classified 269 patients (62%) as dead with melanoma metastasis, 22 (5%) as dead with another malignant tumor, and 92 (21%) as dead with a malignant tumor of uncertain origin. Thirty-eight patients (9%) died with no evidence of malignancy; in 14 cases (3%), the presence or absence of malignancy could not be established due to lack of clinical information. Fair agreement (kappa = 0.34) was observed between the determinations of the MCC based on detailed review of materials and the cause of death reported on the death certificate, but death certificates alone underestimated the proportion of deaths due to metastatic choroidal melanoma. Detailed mortality coding identified difficulties associated with accurate reporting of cause-specific mortality in patients with choroidal melanoma.