Prognostic indicators discriminate patients with good and bad prognosis. Predictive assays are tools that select patients for specific treatments or treatment modifications such that outcome will be improved relative to conventional treatment. In oncology, many prognostic indicators based on clinical or biological tumor characteristics have been described but only very few have proven to be useful as predictive assays. We have developed an imaging modality for coregistration of tumor oxygenation and proliferation at the microregional level with preservation of the tumor anatomy and the microenvironmental structure. We have strong indications that this functional imaging can be a powerful tool for identifying those patients that will profit from hypoxia modifying treatments.