Regional differences in incidence of gastric and colonic cancer in the Maori of New Zealand

Abstract

Background It is known that there are ethnic differences in cancer in New Zealand between Maori (the indigenous people) and non-Maori, however, until now no regional comparisons have been made. Study design A retrospective study of patients diagnosed at Whangarei Hospital, New Zealand between 1995 and 1997 with gastric or colonic cancer was combined with population data from the 1996 census for Whangarei District to calculate incidence figures. The incidence of cancer was compared to national rates. Results Between 1995 and 1997, 19 Maori and 24 non-Maori were diagnosed with gastric cancer, and 10 Maori and 125 non-Maori with colonic cancer. The age standardised rates (per 100 000) for Maori and non-Maori with gastric caner were 68.3 and 7.9 respectively. Gastric cancer is known to be increased in the Maori, but in Whangarei was significantly higher than the national Maori rates (20.5). There was no difference in the rate of colonic cancer in the Maori and non-Maori in Whangarei, again this differs from the national trends, in which the Maori are protected against cancer. Conclusion This study highlights that there is still much more to be learnt in understanding the aetiology of gastrointestinal cancers, to explain such strong regional differences.

Ethnic disparity in colonic cancer outcomes in New Zealand – biology or an access issue?

“…The high incidence and mortality rates of colonic neoplasia in the European population are striking. This pattern has been apparent since the 1970s [5], but the reasons as to why this section of the population should be at such high risk remain unclear [9]. Dietary aetiological hypotheses have been proposed [19], but a study by Smith et al.…”

“…It has long been recognized that within the New Zealand population, there is an ethnic variation in the epidemiology of colonic cancer [5]. Within the limits of ethnic self‐identification (an ever present issue in studies based on registry data) [6,7] there has been a consistently lower rate of colonic neoplasia incidence amongst people of Maori and Polynesian descent compared with rest of the population [1,8,9]. Between 1996 and 2001, the age standardized rate of colonic cancer incidence was 1.5 times higher in non‐Maori than that in Maori populations [10].…”