PET/CT Biological Imaging of Irradiation-Treated Tumors: Which Studies may Lead to an Improvement in Curability?

The growing availability and development of PET/CT imaging has significantly improved the work of all professionals who deal with cancer care: radiologists, clinical oncologists, radiation oncologists and surgeons. The primary use of PET/CT is diagnosis. By using radiotracer-labeled agents that are able to specifically visualize tumor cells or even certain phenomena undergoing in them, significantly more information is delivered. 18FDG is the earliest-introduced and thus the most used PET/CT radiotracer. It basically reflects the intensity of glucose metabolism, which is usually increased in tumors. It therefore reveals all tumor sites and helps differentiate benign and malignant nodules [1]. More tumor-specific radiotracers exist that bind to certain tumors, which demonstrate little 18FDG avidity. These include 11C-choline (prostate cancer), 68Ga-DOTA octreotate (differentiated neuroendocrine tumors, meningiomas), 18F-NaF (bone metastasis) [2]. 18FET detects active DNA synthesis and is the tracer of choice for imaging of the brain tumors and differentiating vivid tumors from inflammatory and post-treatment lesions [3]. Aside from these diagnostic applications, numerous studies are emerging that attempt to derive information on tumor prognosis from PET/CT. Those that may eventually lead to selection of patient subgroups for treatment escalation are particularly important from radiation oncologist’s point of view.