Higher cancer mortality in Mori, Pacific people and native Hawaiians
Indigenous people from New Zealand and Hawaii have higher mortality rates for many cancers than Europeans in those countries according to a publication from the University of Otago, Christchurch. Culturally appropriate education on screening programmes, diet, and smoking might help reduce these mortality rates.
The findings are detailed in the first of a series of literature reviews on worldwide cancer disparities in the latest issue of the prestigious British medical journal 'The Lancet Oncology'. University of Otago Christchurch researcher, Dr Gabi Dachs and colleagues reviewed studies of cancer incidence and mortality, as well as cancer management and risk factors, across Polynesian island populations.
The major finding of the review is that although the likelihood of getting cancer in Mori was not very different from European New Zealanders, the overall likelihood of dying from cancer is about 1.6 times higher in Mori men, and 1.9 times higher in Mori women, than in European men and women in New Zealand.
The authors say: "The incidence of specific cancers differs by ethnic group, with cervical and uterine cancer in women, and stomach and testicular cancers in men being in the top five most common cancers in Mori, but not in non-Mori populations."
Mortality from different types of cancer is higher in Mori and Pacific people than in Europeans, except for colon, brain, and bladder cancer, and melanoma.
For example, for colorectal cancer, the mortality in Mori is similar to that of European New Zealanders despite a much lower incidence of colorectal cancer in Mori.
In Hawaii, a similar pattern is seen, with native Hawaiians having higher cancer mortality than Europeans. Information about cancer incidence and mortality on most other pacific islands is sparse or missing.
Cancer survival (the length of time someone lives with cancer) is also higher in Europeans living in New Zealand and Hawaii than indigenous people.
However, the review does more than describe known extrinsic and individual risk factors which cause differences in cancer mortality. It also raises significant questions as to whether there are differences in the underlying biology of different ethnic groups, i.e. Mori and New Zealand Europeans, which may result in different cancer outcomes.
One of the reasons for these disparities in mortality is that low socioeconomic status is associated with higher cancer mortality, and, generally, Mori and Pacific people have lower incomes than European New Zealanders.
In terms of risk factors, Mori are more than twice as likely to be smokers than European New Zealanders, 50% are more likely to be obese, and almost three times as likely to be obese smokers.
Pacific people living in New Zealand are slightly more likely to smoke, and are much more likely to be obese, than Europeans. Mori and Pacific people also have much higher rates of diabetes than European New Zealanders.
The researchers report that Mori people often present with more advanced stages of cancer than do European New Zealanders, and that screening programmes, e.g. for breast cancer, cover more European than Mori people.
"In some cases, delayed presentation doesn't account for the poorer prognosis of Mori and Pacific Islanders. Future health research needs to focus on the pathological characteristics of specific cancers which indicate a worse prognosis in these ethnic groups," says Dr Dachs.
To tackle the issue of cancer disparity, the New Zealand Cancer Control Strategy Action Plan was implemented in late 2005, consisting of 23 projects. So far, 17 have reported, with some studies recommending specific services for Mori, together with a Mori cancer workforce.
The authors conclude that the extent of the differences in outcome in mortality due to different risk factors, biological factors, or health behaviours is unclear.
They say that evidence exists to support culturally appropriate education on screening programmes, diet, and smoking, all of which could lower the cancer burden in Polynesian communities.
This research was supported by New Zealand Cancer Society, the Health Research Council and the Director's Cancer Research Trust.