Utilizing novel imaging modalities for defining response and predicting long-term outcome after treatment may have a significant impact on cancer patient management. (18)F-FDG PET/CT has great potential for use in early assessment of response to cancer therapy. However, the lack of a general consensus on a specific set of response criteria makes adoption of PET difficult for the oncology community. The optimal time after initiating therapy for assessing response to treatment also has yet to be clearly determined.