Comparison of Cancer Mortality and Incidence Between New Zealand and Australia and Reflection on Differences in Cancer Care: An Ecological Cross-Sectional Study of 2014-2018.

Abstract

Despite many background similarities, New Zealand showed excess cancer deaths compared to Australia in previous studies. This study extends this comparison using the most recent data of 2014-2018. This study used publicly available cancer mortality and incidence data of New Zealand Ministry of Health and Australian Institute of Health and Welfare, and resident population data of Statistics New Zealand. Australian cancer mortality and incidence rates were applied to New Zealand population, by site of cancer, year, age and sex, to estimate the expected numbers, which were compared with the New Zealand observed numbers. For total cancers in 2014-2018, New Zealand had 780 excess deaths in women (17.1% of the annual total 4549; 95% confidence interval (CI) 15.8-18.4%), and 281 excess deaths in men (5.5% of the annual total 5105; 95% CI 4.3-6.7%) compared to Australia. The excess was contributed by many major cancers including colorectal, melanoma, and stomach cancer in both sexes; lung, uterine, and breast cancer in women, and prostate cancer in men. New Zealand's total cancer incidences were lower than those expected from Australia's in both women and men: average annual difference of 419 cases (-3.6% of the annual total 11505; 95% CI -4.5 to -2.8%), and 1485 (-11.7% of the annual total 12669; 95% CI -12.5 to -10.9%), respectively. Comparing time periods, the excesses in total cancer deaths in women were 15.1% in 2000-07, and 17.5% in 1996-1997; and in men 4.7% in 2000-2007 and 5.6% in 1996-1997. The differences by time period were non-significant. Excess mortality from all cancers combined and several common cancers in New Zealand, compared to Australia, persisted in 2014-2018, being similar to excesses in 2000-2007 and 1996-1997. It cannot be explained by differences in incidence, but may be attributable to various aspects of health systems governance and performance.