Research published in The Lancet Oncology, led by the International Agency for Research on Cancer (IARC) on the scale and profile of cancer in indigenous peoples of the USA, Canada, Australia and New Zealand has revealed high rates of often preventable cancers including lung and cervical cancer, emphasising the need for targeted prevention strategies in these populations.

Indigenous people have disproportionally worse health and lower life expectancy than their non-indigenous counterparts in high-income countries.

In this study, the authors investigated and compared, for the first time, the cancer burden among indigenous populations in Australia, New Zealand, Canada, and the USA.

Incidence data were derived from population-based cancer registries in three states of Australia: Queensland, Western Australia (WA), and the Northern Territory (NT); New Zealand; the province of Alberta, Canada; and the Contract Health Service Delivery Areas (CHSDAs) of the USA (where many indigenous peoples of the USA live).

Age standardised incidence rates by registry, year, sex, cancer site, and ethnicity for 2002-06 were compared.

The overall cancer burden was substantially lower in indigenous populations in the USA (except for women in Alaska where it was higher), similar or slightly lower in Australia and Canada, and higher in New Zealand, compared with their non-indigenous counterparts.

The most commonly occurring cancers among indigenous men, irrespective of jurisdiction, were lung, prostate, and colorectal cancer.

Among indigenous women, breast cancer was the most frequent cancer, followed by lung and colorectal cancer.

Of note were the high rates of lung cancer among indigenous men in all Australian regions, New Zealand, and US Alaska natives.

Observed rates were between 44% (Western Australia) and 155% (New Zealand) higher than those observed in non-indigenous men.

Among women, lung cancer rates were also particularly high in New Zealand Māori (four times the rate observed in non-Māori) and Alaska natives (60% higher than in white women).

Cervical cancer incidence was higher among indigenous women in most jurisdictions.

In Australia, head and neck cancers rates were up to 91% higher in indigenous men than in their non-indigenous counterparts.

They were also three and a half times higher among indigenous women in the Northern Territory and twice as high in Alaska natives compared with US white women.

Dr Suzanne Moore, the lead author, commented: "Lower overall incidence in some countries is the result of a lower incidence of several of the most commonly occurring cancers; the reasons for this are not well understood, but probably include competing causes of death at an early age (eg, cardiovascular disease and diabetes) and lower frequency of cancer screening, especially for colorectal and prostate cancers. 30, 31 Other factors such as greater parity, earlier age at first birth, and longer breastfeeding times might contribute to the lower risks of breast cancer."

The study also highlights the harm caused by tobacco in indigenous communities.

Dr Freddie Bray at IARC, and a lead author on the paper, noted that "Lung cancer was the most commonly occurring cancer among indigenous populations in our study. Smoking, a major risk factor for a number of cancers including lung, oral cavity, head and neck, oesophagus, stomach, and cervix appears to be highly prevalent in indigenous communities in all four countries compared to their non-indigenous counterparts."

Dr Christopher Wild, Director of IARC, concluded that "Lung cancer was one of the most commonly occurring cancer in indigenous populations in our study, and in all jurisdictions other than the USA, incidence was higher in indigenous men than in non-indigenous men. Smoking, a major risk factor for various cancers, including of the lung, oral cavity, head and neck, oesophagus, stomach, and cervix,10 is more common in indigenous communities in all four countries than in their non-indigenous counterparts."

Writing in a linked Comment, Associate Professor Diana Sarfati (Director of the Cancer Control and Screening Research Group and Co-Head of the Department of Public Health at Otago University, New Zealand) and Bridget Robson (Associate Dean Māori at the same University) say: "Despite the data shortcomings, Moore and colleagues highlight the striking findings relating to the higher incidence of potentially highly preventable cancers, especially those associated with smoking (eg, lung, and head and neck cancers) and chronic infection (including stomach, liver, and cervical cancers). These findings strengthen the argument for a strategic focus on the burden of cancer in indigenous people, the need for better monitoring, and the development of interventions that address the factors that drive cancer inequities."

Source: The Lancet