Trends in cancer incidence and survival for Indigenous and non-Indigenous people in the Northern Territory

Abstract

Objective: To assess trends in cancer incidence and survival for Indigenous and non-Indigenous Australians in the Northern Territory.

Design: Retrospective analysis of population-based cancer registration data.

Setting: New cancer diagnoses in the NT, 1991-2012.

Main outcome measures: Age-adjusted incidence rates; rate ratios comparing incidence in NT Indigenous and non-Indigenous populations with that for other Australians; 5-year survival; multivariable Poisson regression of excess mortality.

Results: The incidence of most cancers in the NT non-Indigenous population was similar to that for other Australians. For the NT Indigenous population, the incidence of cancer at several sites was much higher (v other Australians: lung, 84% higher; head and neck, 325% higher; liver, 366% higher; cervix, 120% higher). With the exception of cervical cancer (65% decrease), incidence rates in the Indigenous population did not fall between 1991-1996 and 2007-2012. The incidence of several other cancers (breast, bowel, prostate, melanoma) was much lower in 1991-1996 than for other Australians, but had increased markedly by 2007-2012 (breast, 274% increase; bowel, 120% increase; prostate, 116% increase). Five-year survival was lower for NT Indigenous than for NT non-Indigenous patients, but had increased for both populations between 1991-2000 and 2001-2010.

Conclusion: The incidence of several cancers that were formerly less common in NT Indigenous people has increased, without a concomitant reduction in the incidence of higher incidence cancers (several of which are smoking-related). The excess burden of cancer in this population will persist until lifestyle risks are mitigated, particularly by reducing the extraordinarily high prevalence of smoking.