Abstract
BACKGROUND: Anatomical site is strongly associated with head and neck cancer etiology, and etiology and patient sociodemographic characteristics are prognostic factors for survival. It is not known whether the effects of these predictors persist over the postdiagnosis period or are strongest proximal to the time of diagnosis. METHODS: Using survival times and causes of death for 180,434 patients with head and neck cancer in the Surveillance, Epidemiology, and End Results cancer registry (1973-2015), the empirical cumulative incidences of cancer-specific death and other-cause death were calculated with a competing risks framework, and the time-dependent effects (hazard ratios) of anatomical tumor site (oropharynx, oral cavity, or hypopharynx/larynx), age, sex, race, and year of diagnosis on cancer-specific death and other-cause death, stratified by tumor stage, were estimated. RESULTS: All effects were significantly time-varying (P < .001). Patients with nonoropharyngeal cancer had a higher hazard of cancer-specific death but a similar cumulative fraction of deaths because of a higher rate of death from other causes. Cancer-specific survival has not changed for patients with nonoropharyngeal cancer over the past decades but has improved since 2000 for patients with oropharyngeal cancer. The effects of age and sex on cancer survival were strongest proximal to the diagnosis, whereas the effect of race persisted over time. CONCLUSIONS: Recent improvements in survival for patients with oropharyngeal cancer may be due more to an increasing fraction of cancers attributable to human papillomavirus than to increasing treatment effectiveness. The prognostic strength of anatomical site and other predictors changes over the postdiagnosis period. LAY SUMMARY: It is generally assumed that the effects of tumor and personal characteristics on the survival of patients with head and neck cancer are fixed over time, but this study shows that many factors are most important only in the first few years after diagnosis. Also, recent improvements in the survival of patients with head and neck cancer appear to benefit only patients with cancers of the oropharynx. The improvements may be due more to an increasing fraction of cancers caused by human papillomavirus (which generally have better outcomes) than to advances in head and neck cancer treatment overall.