Interim18FDG PET/CT during radiochemotherapy in the management of pelvic malignancies : a systematic review

18F-fluorodeoxyglucose PET/CT (18F-FDG-PET/CT) is widely applied in oncology for disease staging, assessment of therapy response, relapse diagnosis, follow-up and target volume delineation. In particular, it can detect early response during chemoradiotherapy (interim) because functional modifications usually precede morphological ones. This ability is crucial to the radiation oncologist for the management of patients, to avoid persisting with ineffective therapy - often leading toxicity - and to shift to potentially more effective alternatives. Interim 18F FDG-PET imaging in rectal and cervical cancer, the main malignancies of the pelvic district, has been applied and a broad literature is available, although some results are discordant. This systematic review summarizes the application of 18F FDG-PET/CT during the chemoradiotherapy of locally advanced pelvic malignancies in order to clarify its capability to predict response and prognosis and its potential role to tailor therapy, which seems to be validated in rectal cancer, whilst less conclusive in cervical cancer.