Clinical biomarkers and imaging for radiotherapy-induced cell death.

INTRODUCTION: Radiotherapy, like most anticancer treatments, achieves its therapeutic effect by inducing different types of cell death in tumors. CELL DEATH MARKERS AND IMAGING MODALITIES: To evaluate treatment efficacy a variety of routine anatomical imaging modalities is used. However, changes in tumor physiology, metabolism and proliferation often precede these volumetric changes. Therefore, reliable biomarkers and imaging modalities that could assess treatment response more rapidly or even predict tumor responsiveness to treatment in an early phase would be very useful to identify responders and/or avoid ineffective, toxic therapies. A better understanding of cell death mechanisms following irradiation is essential for the development of such tools. CELL DEATH AND AVAILABLE ASSAYS: In this review the most prominent types of radiation-induced cell death are discussed. In addition, the currently available assays to detect apoptosis, necrosis, mitotic catastrophe, autophagy and senescence in vitro and, if applicable, in vivo, are presented.