Stage at diagnosis for Māori cancer patients: disparities, similarities and data limitations

Māori are more likely than non-Māori to get cancer, and once they have cancer they are less likely to survive it. One frequently proposed explanation for this survival disparity is differences between these groups in terms of stage at diagnosis-whereby Māori may be less likely to be diagnosed at an earlier stage, when treatment is more feasible and outcomes are better for the patient. However, this simple explanation ignores the true complexity of the issue of stage at diagnosis as a driver of survival disparities, and makes critical assumptions about the quality of available staging data. In this manuscript we draw on New Zealand Cancer Registry and available clinical audit data to explore this issue in detail. We found that Māori are less likely than European/Other patients to have localised disease and more likely to have advanced disease for several commonly diagnosed cancers; however, we also found that this was not the case for several key cancers, including lung and liver cancer. There is evidence that Māori have more advanced disease at diagnosis for each of the cancers for which we currently have a national screening programme, reinforcing the importance of achieving equity in access to these programmes. Missing stage information on our national registry undermines our ability to both a) monitor progress towards achieving early diagnosis, and b) examine and monitor the role of stage at diagnosis as a driver of survival disparities for several important cancers for Māori, including lung, liver and stomach cancers.