The signaling pathways in solid tumors are very complex and many. Cancer cells can use any of dozens of biochemical pathways to proliferate and spread. Stop one pathway and the cells can turn on a different pathway. And the more recalcitrant tumors have redundant systems to let them escape from numerous anti-cancer agents.

A goal is the choose therapies so they target the precise proliferation pathways the cancer is using. We have the ability to profile tumors so that oncologists would know not to use one particular drug (or combinations of drugs) because it won't help, but utilized some other particular drug (or combination) because it shows that it is synergistic (cooperative) to the cancer cells (killing them).