By 2020, 15 million people worldwide will have cancer and nine million of them will be living in developing countries, according to World Health Organization estimates. Harvard University physician and medical anthropologist Paul Farmer is determined to ensure that prediction doesn’t come true. Farmer, a pioneer in global health, has a history of tackling big problems. His Ph.D. dissertation on HIV in Haiti ran to 1,000 pages, leading Harvard to impose a cap. Since then, as co-founder of the nonprofit Partners In Health, he has brought medical treatments, from basic primary care to antiretroviral therapies for AIDS, to millions of the world’s poor.