Cancer survival rates in New Zealand have improved by more than 25 per cent in each of the last two decades, a new report has found.

Otago University researchers say the improvement is a success story but also point to stark inequalities between Maori and non-Maori in chances of surviving cancer .

The CancerTrends report, released today, looked at people diagnosed with 21 different cancers from 1991 to 2004 and examined whether they had died by the end of 2006.

Researchers from the university's department of public health matched the findings with census data to give the first accurate analysis of trends by ethnicity and household income.


Professor Tony Blakely said the death rate, averaged across all cancers, had reduced by 26 per cent every decade.

The death rate was measured over and above what could be expected given the person's sex, age, ethnicity and income level.

"This is a success story, and a tribute to our improving health services," Prof Blakely said.

"The bad news, though, is that the large differences in survival between Maori and non-Maori didn't change over time."

While both groups showed improvements in survival, the excess mortality rate among Maori remained about 29 per cent higher across time. "This is a challenge for the health sector - how to get even greater gains in survival for Maori so that gaps close."

The report did not directly address the reasons for the overall decline in the death rate but reasons would include earlier diagnosis, improved surgical treatments, more effective drugs and generally better care.

Cancers with particularly strong improvements in survival include breast cancer, which saw a 52 per cent decrease in the death rate every decade, leukaemia, with a 60 per cent decrease, and non-Hodgkin's lymphoma, with a 44 per cent decrease.

Other cancers, such as lung and pancreatic cancer, showed little improvement.

The report also highlighted inequalities in survival between different income levels.

People diagnosed with cancer in the lowest third of household incomes had a 12 per cent higher excess mortality rate than people with high income when averaged over time.

Reductions in the excess mortality rate among low income people were slower than high income people, with the gap widening by about 9 per cent every decade.

The study was funded by the Health Research Council with support from the Ministry of Health.