Background and purpose: Preoperative chemoradiation allows downstaging of locally advanced rectal cancer and in selected patients also a sufficient downsizing to ensure sphincter preservation. Selection of patients warranting a preoperative approach is improved by magnetic resonance imaging (MRI) which is able to define the involvement of mesorectal circumferential margin. Similarly it would be crucial to define the response to chemoradiation during the treatment but traditional morphologic imaging techniques may fail in differentiating neoplastic tissue from scarring. PET-FDG has been successfully used in the detection of metastatic colorectal cancer allowing imaging of deposits as small as 0.5 cm and may have a role in evaluating early response to chemoradiation.
Methods: In the present study, in patients with T3-T4 rectal cancer undergoing preoperative chemoradiation PET-FDG and flow cytometry analysis on endoscopic biopsy specimen have been performed before, during and after preoperative chemoradiation.
Results: Chemoradiation treatment has been successful in terms of downsizing and downstaging of the tumor. PET-FDG was able to demonstrate local response at only ten-fifteen days after the beginning of neoadjuvant therapy, also identifying non responding patients.
Conclusions: FDG-PET may have a role in defining the response to chemoradiation and modulate the treatments strategy in patients with advanced rectal cancer.