18FFAZA imaging will be performed in all patients after overnight fasting on a dedicated full ring PET scanner (Advance, General Electric Medical Systems, Milwaukee, WI). The patients will be scanned subsequent to the administration of the activity (dynamic scan) and 2 hours afterwards (static scan). For each image acquisition a 10-min transmission scan will be performed. All images will be acquired in a 3D-mode with a matrix of 128x128. The dynamic scan (pelvis) begins with the intravenous administration of 370 MBq 18FFAZA. Over the first hour 21 frames will be acquired (6 frames 20s, 6 frames 30s, 2 frames 150s, 4 frames 300s, 3 frames 600s). Two hours after the application a 10-min static scan (pelvis + abdomen) will be acquired. The images are reconstructed using an iterative algorithm (OSEM). In addition to visual interpretation of the acquired images a semi quantitative analysis will be performed by drawing regions of interest (ROIs) in tumor tissue (primary and lymphnodes). For these ROIs both a standardized uptake value (SUV) and ratios to normal tissue (muscle) will be calculated.