Drug resistance in cancer, whereby a portion of cancer cells evades chemotherapy, poses a profound and continuing challenge for the effective treatment of cancer. The principles underlying the biological mechanisms behind this phenomenon are clearly explained in this volume. A deeper understanding of drug resistance requires a quantitative appreciation of the dynamic forces that shape tumor growth, including spontaneous mutation and selection processes. The authors seek to explain and to simplify these complex mechanisms, and to place them in a clinical context. Clearly explained mathematical models are used to illustrate the biological principles and provide an insight into tumor development and the effectiveness and limitations of drug treatment. The volume is suitable for those with a nonmathematical background and aims to enhance the effectiveness of cancer therapy. This is the first book to provide such an integrated account, in a form accessible to both doctor and scientist.