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The prevalence of rare cancers varies geographically, and this study displays how much of a public health burden these cancers are when looked at collectively.

Rare cancers, despite occurring less commonly, account for a quarter of total cancer diagnoses and deaths in the US, Europe, and Australia. Few epidemiological studies have analyzed the distribution and causes behind rare cancer mortality and incidence; however, their collectively high incidence makes their share of the total cancer burden a significant clinical concern. 

Because rare cancers are a very heterogeneous group, gathering data about their individual properties can be both difficult and limited in their applications. A 2022 study published in the International Journal of Cancer analyzes the geographic distribution patterns in both the incidence and survival of rare cancer types in Australia.

For this study, rare cancers were classified using site- and histology-based categories derived from the European RARECARE consortium’s RARECARE list. Cancer types that have a crude annual incidence rate of under 6 in 100,000 were thus defined as rare. Data for the study were gathered from a population-based cancer registry cohort of rare cancers diagnosed among Australian patients aged 15 years and up, between 2007 and 2016. 

The Significant Collective Burden of Rare Cancers 

In order to analyze incidence and survival patterns, generalized linear and Bayesian spatial Leroux models were used. The total number of rare cancer cases found during the study was 268,070, which collectively comprised 22% of all invasive cancer diagnoses during the time period of the study and accounted for 27% of all cancer-related deaths in Australia. The 5-year relative survival rate for rare cancers was reported as 51–56%, which is similar to statistics in the US and Central and Northern Europe. Those living in remote areas were found to both exhibit higher incidence and lower survival.

Both incidence and survival of rare cancers as a whole varied geographically throughout the country. Additionally, this pattern uniformly showed that areas with higher incidence also exhibit lower rates of survival. In addition to those living in remote areas, patients who were socioeconomically disadvantaged exhibited higher incidence and worse survival compared to their counterparts. This combination of factors serves to magnify the geographic and socioeconomic disparity that is present with these cancers.

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Understanding the Logistic Challenges to Serving Disadvantaged Cancer Patients 

The reason for these disparities can be partially attributed to a lack of cancer care available outside of major cities. Due to the size and geographic diversity of Australia, patients in rural areas may have to travel significant distances to obtain care, and these effects are likely magnified for rare cancers compared to those that are more common. Disadvantaged Australians are also reported to more commonly engage in lifestyle-related health risk behaviors, which can further magnify the problem. The findings in this study highlight the need to understand the higher burden that rare cancers pose to disadvantaged populations, while also displaying the need for solutions to the logistic issues that face these populations’ access to care.

Source:

Dasgupta, P., Cameron, J. A., Cramb, S. M., Trevithick, R. W., Aitken, J. F., Mengersen, K., & Baade, P. D. (2022). Geographical and spatial disparities in the incidence and survival of rare cancers in Australia. International Journal of Cancer, 152(8), 1601–1612. https://doi.org/10.1002/ijc.34395