Inaccuracies in oral cavity-pharynx cancer coded as the underlying cause of death on U.S. death certificates, and trends in mortality rates (1999-2010).

OBJECTIVE: To enhance surveillance of mortality from oral cavity-pharynx cancer (OCPC) by considering inaccuracies in the cancer site coded as the underlying cause of death on death certificates vs. cancer site in a population-based cancer registry (as the gold standard).
METHODS: A database was used for 9 population-based cancer registries of the Surveillance, Epidemiology and End Results (SEER) Program, including deaths in 1999-2010 for patients diagnosed in 1973-2010. Numbers of deaths and death rates for OCPC in the SEER population were modified for apparent inaccuracies in the cancer site coded as the underlying cause of death.
RESULTS: For age groups <65 years, deaths from OCPC were underestimated by 22-35% by using unmodified (vs. modified) numbers, but temporal declines in death rates were still evident in the SEER population and were similar to declines using routine mortality data for the entire U.S. population. Deaths were underestimated by about 70-80% using underlying cause for tonsillar cancers, strongly associated with human papillomavirus (HPV) infection, but a lack of decline in death rates was still evident.
CONCLUSION: Routine mortality statistics based on underlying cause of death underestimate OCPC deaths but demonstrate trends in OCPC death rates that require continued surveillance in view of increasing incidence rates for HPV-related OCPC.