Methodological Aspects and Applications of In Vivo Imaging of Apoptosis in Oncology: An Illustrative Review

In vivo monitoring of apoptosis during anticancer therapy has attracted intense research interest as a potential assay to predict treatment outcome. From all apoptosis-detecting radioligands, the group of Annexin V-based tracers is currently the most widely used for real time imaging of apoptosis in patients with various malignant and non-malignant diseases. In this article, we discuss the current status of in vivo imaging of apoptosis by means of 99mTc -Annexin V scintigraphy: the biodistribution of the tracers will be illustrated and the methodological aspects of gamma camera imaging procedure will be outlined. In addition, recently developed phosphatidylserine-targeting tracers for PET imaging of programmed cell death will be highlighted. We will specify the opportunities to improve visual assessment of the scintigraphic images. A four-step grading scale and SPECT/SPECT, SPECT/CT and SPECT/MRI fusion models will be discussed in order to overcome technical limitations caused by low tumour-to-background ratio. Furthermore, possible clinical applications of this technique in oncology will be illustrated in detail, with a major accent on the group of patients with malignant lymphoma, lung cancer and head and neck squamous cell cancer.