That's not even true if you look only at rich countries - cardiovascular diseases cause more deaths.
The amount of effort, let alone money, spent on cancer research is already obscene compared to what is spent on other serious problems.
cancer.org states that 15% of deaths worldwide are due to cancer, with 50% being spread amongst other non-communicable diseases.
http://www.cancer.org/research/infographics/rising-global-ca...
"In 2010, 65% of all deaths worldwide were due to noncommunicable diseases (NCDs) like heart disease, lung disease, diabetes and cancer. 15% of all deaths worldwide, nearly 8 million people, were due to cancer alone. The number of deaths worldwide from cancer dwarfs the number of global deaths from malaria and HIV/AIDS, as is projected to exceed 13 million by 2030."