Applying the recursive partitioning method as an exploratory analysis resulted in a cut-off point of 23% for the proportion of Aboriginals per health region. For distance to nearest radiotherapy centre, a cut-off was identified at 37 kilometres for health regions with <23% Aboriginals, and 922 kilometres for health regions with ≥ 23% Aboriginals (Figure 2). There were no health regions inhabited by ≥ 23% Aboriginals that were less than 200 kilometres from the nearest radiotherapy centre (Figure 3); therefore, the recursive partitioning algorithm identified two different cut-off points, one for health regions with a higher proportion of Aboriginals, and one for a lower proportion.