Radiolabelled chemotherapeutics

During the past 3 decades various chemotherapeutics have been directly or indirectly radiolabeled for single photon emission computed tomography (SPECT) and positron emission tomography (PET) imaging. Several of these radiolabeled chemotherapeutics have been injected into patients for the purpose of better understanding their biodistribution and metabolism and to assess whether there exists a relationship between their uptake in tumor tissue and response to treatment. Based on available data, it may be concluded that PET or SPECT imaging with radiolabeled chemotherapeutics provides valuable information that helps to better understand the mechanism of action and the metabolic conversion of unlabeled chemotherapeutics in humans and that helps to provide a rationale for the lack of response to certain chemotherapeutics or for the beneficial effect of biomodulating agents. As for their utility as predictors of response to therapy, their utility is limited to those agents given in monotherapy.