The most comprehensive comparison of worldwide cancer data ever published has uncovered some striking disparities, highlighting both the extremely low survival rates in some countries, and also the large differences in treatable cancers. Among the starkest examples are differences in net survival of childhood acute lymphoblastic leukemia – ranging from just 16 percent in Jordan to 80–90 percent in Canada and many parts of Europe (1). However, huge variations aren’t only seen in the divide between developing and developed countries, which one would expect – even within Europe, survival rates vary significantly.
The study, published in The Lancet, includes data from 279 cancer-based registries, originating from 67 countries (23 of which are considered low or middle income), and involving 25.7 million adults and 75,000 children – accounting for roughly two-thirds of the world’s population. Ten common adult cancers were included: stomach, colon, rectum, liver, lung, breast, cervix, ovary, prostate, and adult leukemia. The authors found that survival of some cancers was universally low; less than 20 percent for lung and liver cancer in almost every country studied, demonstrating that both conditions are still lethal in the majority of cases. Unsurprisingly, the numbers also demonstrate that in most cases, patients in developing countries were much less likely to survive all types of cancer. What might have been less expected is the variation observed between developed nations. An illustrative example is stomach cancer net survival from 2005 to 2009 – this was highest in Korea and Japan (58 percent), while for some countries with comparably well-equipped healthcare systems it was less than half that – under 25 percent in Canada, Norway, The Netherlands and the UK (see Chart). The authors note that this is likely to be down to more intense diagnosis and radical surgery; cancer types with a more favorable prognosis may also be more common in these countries. Conversely, survival of leukemia in East Asian countries is low (19 percent in Japan) when compared with many European countries (40 to 60 percent).
On a more positive note, prostate cancer survival has seen marked increases; 22 countries saw a 10 to 20 percent rise in the last 20 years, but the gap is still wide – under 60 percent survival in Thailand, versus more than 90 percent in Brazil and the US. Even when making allowance for artefacts and comparison problems in such a large dataset, the numbers make it clear that successful treatment of cancer is not simply a question of medical resources – attitudes to screening and treatment, political forces, public awareness and genetic predispositions of the population in question could all potentially come into play when it comes to surviving cancer, no matter where you live.
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References
- C. Allemani et al., “Global Surveillance of Cancer Survival 1995–2009: Analysis of Individual Data for 25676887 Patients From 279 Population-Based Registries in 67 Countries (CONCORD–2)”, Lancet, [epub ahead of print] (2014).