In this episode, I’ll continue to discuss the evaluation of response to therapy using PET. A number of factors affect when to assess therapy response and how to interpret the results, and there are differences between radiation therapy and chemotherapy. Within radiation therapy, it is very important to consider the particular disease, so I’ll discuss specifics for ovarian, cervical, lung, colorectal, and liver cancer. Most of this discussion uses data on the popular FDG tracer, but I will also mention some of what we have to look forward to with newer isotopes.