The figures were extrapolated from an observed rise in cancer deaths for every percentage increase in unemployment, and every drop in public healthcare spending.
"From our analysis we estimate that the economic crisis was associated with over 260,000 excess cancer deaths in the OECD (34-member Organisation for Economic Cooperation and Development) alone, between 2008-2010," study author Mahiben Maruthappu of Imperial College London told AFP.
"This suggests that there could have been well over 500,000 excess cancer deaths worldwide during this time."
For the European Union alone, the estimate was 160,000 additional deaths -- a term used to describe people who would not otherwise have died.
For the United States, the estimate was 18,000 and for France 1,500. For Spain and Britain, which provided universal healthcare, no additional deaths were calculated.
The study was published in The Lancet medical journal.
"Cancer is a leading cause of death worldwide so understanding how economic changes affect cancer survival is crucial," Maruthappu said.
In 2012, cancer caused some 8.2 million deaths.
"We found that increased unemployment was associated with an increased cancer mortality, but that universal health coverage protected against these effects," Maruthappu said.
"This was especially the case for treatable cancers including breast, prostate and colorectal cancer."
The researchers used World Health Organization and World Bank statistics on more than 70 countries with over two billion inhabitants to analyse the link between unemployment, public healthcare spending and cancer mortality.
They analysed the trend over 20 years from 1990 to 2010.
They found that every one-percent increase in unemployment was associated with 0.37 additional cancer deaths per 100,000 people.
- 'Case for universal coverage' -Every one-percent drop in healthcare spending was associated with 0.0053 additional deaths per 100,000 people.
They then used this data to extrapolate additional deaths from 2008-2010, noting that the economic crisis saw a "substantial rise" in unemployment and cuts in healthcare spending in many countries.
"In countries without universal health coverage, access to healthcare can often be provided via an employment package," said co-author Rifat Atun of Harvard University.
"Without employment, patients may be diagnosed late, and face poor or delayed treatment."
In a comment on the study, US-based researchers Graham Colditz and Karen Emmons wrote that the data "make a strong case for universal health coverage and its protective effect on cancer mortality."