Determining Cause of Death in Prostate Cancer: Are Death Certificates Valid?

Accurate assessment of cause of death (COD) is important for determin-ing cause-specific survival in cancer re-search. It is possible to reliably ascertain COD by meticulous review of inpatient and outpatient medical records with the use of predetermined clinical algorithms (1). Unfortunately, this method, al-though useful for small retrospective studies, is impractical for large datasets and national tumor registries that are commonly used for cancer research. When these large databases are used, COD is assigned with a standardized de-cision algorithm that uses International Classification of Diseases, ninth revi-sion (2), codes to assign both immediate and underlying COD (3). However, this methodology is unreliable (4,5), particu-larly when patients are older or have considerable comorbidity, as is the case in prostate cancer (6,7). In a study of mortality trends, Grulich et al. (8) esti-mated that inaccuracies in death certifi-cation and coding accounted for up to 46 % of the noted increase in prostate cancer mortality seen in England and Wales from 1970 through 1990. By con-trast, in men with prostate cancer iden-tified through the Connecticut Tumor Registry, Albertsen et al. (9) found a high level of agreement between the un-derlying COD, determined by a review of the medical records, and death certif-icate data. It is important that prostate cancer-related mortality ascertained by death certificate be reliable because studies that use large datasets, such as the Surveillance, Epidemiology, and End Results (SEER)1 Program, may be used to determine whether interventions (e.g., screening, radical prostatectomy, or radiotherapy) are effective. This study assessed whether the un-derlying COD on death certificates for men with prostate cancer agreed with an independent review of inpatient medical records in a sample of prostate cancer patients who died in King County, WA, in 1995. Our goal was to assess the va-lidity of the coding system currently used by each state for determining un-derlying COD from death certificate data that are submitted to the National