Cancer
Since World War II, scientists have kept finding better cancer treatments. However, there are some things that still need to get better. For example, while there are good treatments for many kinds of cancer, there are still no treatments for certain kinds of cancer, or for some cancers once they progress (or get worse) to a certain stage of the disease. Also, the cancer treatments that do exist are not all standardized (there is not one agreed-upon way of giving every treatment which is used each time the treatment is given). Cancer treatments are also not available everywhere in the world.  People need to keep studying cancer epidemiology and forming international partnerships (where different countries work together) to find cures and make cancer treatments available everywhere.