We certainly do have to be realistic about where we stand. It is the case that cancer is the second-leading cause of deaths in the U.S., in fact, in nearly half the states it's the leading cause of death. And we have a ways to go.

The challenge is that if you stimulate your immune system, it might get over-stimulated. And it might actually start causing harm to normal cells in your body. So we have to work a balance between attacking the cancer and not attacking yourself.

Actually, as cancers develop in an individual patient, an individual cancer cell might be different - a little bit different - from the cell that's sitting right next to it. And so there's heterogeneity, we call it. It makes the problem that much harder.

We are living through a remarkable time where we're translating this investment that we've made in cancer science to new treatments. And they're benefiting a large number of people and they will benefit many more in the years to come.

Cancer is complex and therefore there is not a one-size-fits-all solution.

We certainly do have to be realistic about where we stand. It is the case that cancer is the second-leading cause of deaths in the U.S., in fact, in nearly half the states it's the leading cause of death. And we have a ways to go.