Socio-economic disadvantage and cancer survival disparities

A study published today in BMC Public Health has found that people living in socio-economically disadvantaged areas in New South Wales (NSW), Australia, have a higher risk of cancer death. In this blog Dr Hanna Tervonen, one of the authors of the study explores the complex factors behind this disparity.

In the face of cancer, people are not all equal. An individual’s likelihood of survival following a cancer diagnosis depends on many factors. These include tumor characteristics, such as site, size and spread; demographic factors such as age; but also where people are born and live along with the conditions of daily life – the so called social determinants of health. This broader environment impacts on how healthy our lives are, how early cancer is detected and what kind of treatment we receive.

We examined comparative cancer survival in New South Wales (NSW), the most populous state in Australia, over a 30-year period and identified higher risk of cancer death for those living in socio-economically disadvantaged areas and outside major cities. These survival disparities remained when we took into account differences in age, cancer stage at diagnosis, potential other causes of deaths, and differences in cancer site between population groups.

Disparities in cancer survival may be explained by factors that we cannot easily measure when using data from cancer registries. Factors that our study could not take into consideration included comorbidities, health behaviors, social support, and clinical cancer care. These factors are likely to impact overall cancer survival and any survival differences.

Quality of treatment

New treatment options and technologies, as well as clinical trials of new treatments may be less accessible to deprived population groups

Treatment is an important factor to consider when assessing cancer survival differences. There is evidence that disadvantaged population groups may receive less optimal treatment. New treatment options and technologies, as well as clinical trials of new treatments may be less accessible to deprived population groups.

Although we could not determine how much survival differences found in our study were driven by varied access to and/or quality of treatment, a universal health care system is expected to diminish some differences in health status between population groups. Despite the universal health care system in Australia, people with lower socio-economic status had worse cancer outcomes in NSW.

The findings from our study are unlikely to be specific to NSW or Australia. In fact, the association between lower socio-economic status and lower cancer survival has been demonstrated in several countries, including other countries which also have universal health coverage and extensive social safety nets. This further highlights that cancer survival disparities are not entirely explained, nor fixed, by health care system related factors; a broader socio-economic context appears to be exerting an influence.

In NSW, the comparative risk of cancer death in people living in socio-economically disadvantaged areas has increased over time. Cancer survival has improved over time for everyone but it seems that improvements have been greater or happened more quickly for well-off people, and consequently the survival gap has increased.

Cancer survival in migrants

We also examined cancer survival by migrant status and grouped people based on their country of birth into those from English-speaking and non-English speaking countries. Australia has a large migrant population with more than a quarter of the population born outside Australia.

Migrant groups may be disadvantaged in terms of health outcomes due to cultural, linguistic and health literacy barriers. However, according to our results, people born in other English-speaking countries had a similar risk, and those born in non-English speaking countries had a lower risk of cancer death compared with the Australian-born.

According to our results … those born in non-English speaking countries had a lower risk of cancer death compared with the Australian-born

This is perhaps surprising especially if we assume that language skills are associated with capacity to navigate through the health system, and that these navigation skills translate into better health outcomes.

It is likely that better survival in people born in non-English speaking countries is partly artefactual. Migrants are commonly healthier than the general population (so called ‘healthy migrant’ effect). They may also return to their home countries for the final stages of their life, so that information about their deaths won’t be recorded in the country where they were diagnosed with cancer.

Considering our previous findings that people born outside Australia had slightly higher risk of being diagnosed with advanced stage cancer, loss to follow-up appears to be a plausible explanation for recorded cancer survival advantage for some migrant groups in our study.

Socio-economic disadvantage is a complex concept with no consensus on how best to measure it. Several factors, including education, income, employment and family background have differing and likely culture-dependent effects on a person’s socio-economic status. We measured socio-economic disadvantage using an area-based measure which may not correspond to individual’s social class or position.

To be able to develop targeted actions and interventions, a more in-depth understanding of reasons driving socio-economic differences in cancer survival is needed. Such factors are likely to lie outside the direct responsibility of the health sector. Therefore, properly resourced and co-ordinated input from service providers from different sectors is essential for closing the socio-economic cancer survival gap.

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