Head and neck cancer incidence and two-year mortality in Aotearoa New Zealand, 2009–2020: a national population-based cohort study

BACKGROUND: Head and neck cancer (HNC) imposes a substantial burden in Aotearoa New Zealand (AoNZ), yet contemporary population-level data on incidence and early mortality across sociodemographic groups remain limited. METHODS: This population-based retrospective cohort study used New Zealand Cancer Registry to identify all primary HNC diagnoses from 2009 to 2020 (n = 6980). The cases were classified according to ICD-10 subsites. Incidence rates (IRs), age-standardised IRs, and age-standardised rate ratios were estimated by age, sex, ethnicity, socioeconomic deprivation, and rurality. Regression models were used to estimate annual percentage change in IRs and to estimate adjusted risk ratios for two-year all-cause mortality. RESULTS: In total 6980 people were diagnosed with HNC; an overall incidence rate of 13.5 per 100,000 person-years (PY). Oropharyngeal cancer (OPC), the most common subsite, increased from 3.4 per 100,000 PY in 2009-2011-4.9 per 100,000 PY in 2018-2020, whereas IRs for oral cavity cancer (OCC), the second most common, were more stable. HNC IRs were higher among males, older adults, Māori, Pacific Peoples and people living in the most socioeconomically deprived areas, with subsite-specific differences: Māori experienced higher OPC incidence rates, while Pacific Peoples experienced higher OCC IRs. Within two years of diagnosis, 25.2% of patients had died. Two-year all-cause mortality was 44.4% for hypopharyngeal cancer, 30.9% for OCC, and 22.7% for OPC. Among people diagnosed with HNC, after adjusting for available sociodemographic factors and treatment timing, two-year all-cause mortality was higher for Māori, Pacific Peoples, and those in the most deprived quintile. Rurality showed no consistent association with incidence or two-year mortality. CONCLUSIONS: These findings indicate an OPC-driven shift in HNC epidemiology in AoNZ and a persistent inequitable burden of both disease occurrence and early mortality, supporting stronger surveillance and equity-focused cancer-control responses.