Cancer survival is significantly improving in New Zealand, but inequalities in survival remain stark according to a new report released today by the University of Otago and the Ministry of Health.
The researchers have investigated survival over 21 different cancers for people diagnosed from 1991 to 2004, and followed up for possible death till the end of 2006. This data was then linked to census data, allowing accurate analyses for the first time of trends by ethnicity and household income.
The researchers from the Department of Public Health at University of Otago, Wellington, measured the death rate amongst cancer patients over and above that expected given the person's sex, age, ethnicity and income level – that is the excess mortality.
“The good news is that averaged across all cancers, the death rate among those diagnosed with cancer reduced by 26% every decade,” says Professor Tony Blakely. “This is a success story, and a tribute to our improving health services.”
Reasons for this decline were not directly assessed in the CancerTrends Report, but will include earlier diagnosis, improved surgical treatments, more effective drugs, and generally better care.
Cancers with particularly strong improvements in survival include breast (52% decrease every decade in death rate among those diagnosed), leukaemia (60%) and non-Hodgkin's lymphoma (44%). However, other cancers such as lung and pancreatic have showed little improvement over time.
“The bad news, though, is that the large differences in survival between Maori and non-Māori didn't change over time,” he says.
Whilst both Māori and non-Māori enjoyed large improvements in survival, excess mortality remained about 29% higher amongst Māori across time. “This is a challenge for the health sector – how to get even greater gains in survival for Māori so that gaps close.”
Inequalities in survival were also seen between different income levels. People diagnosed with cancer in the lowest third of household incomes had a 12% higher excess mortality rate than people with high income when averaged over time. However, there was also a statistically significant trend for reductions in excess mortality to be slower among low income people than high income people, such that the gap is opening up by about 9% every decade.
The CancerTrends study was funded by the Health Research Council of New Zealand, with support from the Ministry of Health. The report and executive summary can be accessed from:
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