Cancer patients often endure a battery of different drug treatments to find a therapy that works. Scientists have known for some time that genetics help explain why certain drugs may work on one person and not on another, but new findings by KI members Michael Hemann and Doug Lauffenburger suggest that the timing of these treatments may also be a critical factor. Tumors evolve through various stages, and the team’s study shows that sensitivity to a particular drug can depend on the stage at which it is administered. Their findings indicate that there may be windows of opportunity for drugs that had previously been written off as failures for individual patients. Hemann and Lauffenburger hope that modeling methods will predict tumor evolution and improve targeted therapies to help combat drug resistance. This research was supported in part by the Go Mitch Go Foundation.