Impact of using multiple causes of death codes to compute site-specific, death certificate-based cancer mortality statistics in the United States

Background: Cancer mortality statistics, an important indicator for monitoring cancer burden, are traditionally restricted to instances when cancer is determined to be the underlying cause of death (UCD) based on information recorded on standard certificates of death. This study's objective was to determine the impact of using multiple causes of death codes to compute site-specific cancer mortality statistics. Methods: The state cancer registries of California, Colorado and Idaho provided linked cancer registry and death certificate data for individuals who died between 2002 and 2004, had at least one cancer listed on their death certificate and were diagnosed with cancer between 1993 and 2004. These linked data were used to calculate the site-specific proportion of cancers not selected as the UCD (non-UCD) among all cancer-related deaths (any mention on the death certificate). In addition, the retrospective concordance between the death certificate and the population-based cancer registry, measured as confirmations rates, was calculated for deaths with cancer as the UCD, as a non-UCD, and for any mention. Results: Overall, non-UCD deaths comprised 9.5 percent of total deaths; 11 of the 79 cancer sites had proportions greater than 3 standard deviations from 9.5 percent. The confirmation rates for UCD and for any mention did not differ significantly for any of the cancer sites. Conclusion and impact: The site-specific variation in proportions and rates suggests that for a few cancer sites, death rates might be computed for both UCD and any mention of the cancer site on the death certificate. Nevertheless, this study provides evidence that, in general, restricting to UCD deaths will not under report cancer mortality statistics.