Rectal operative bed: ?tumor? post-management changes … positron emission tomography/computed tomography (PET/CT) can answer

Abstract

Background: Rectal cancer is a common malignancy that continues to have a highly variable outcome. Local pelvic recurrence following surgery is usually leading to incurable disease. Surgical resection with stage-appropriate combined-modality therapy is the mainstay in the treatment of rectal cancer. A difficulty has been reported in distinguishing the benign post-management findings from tumor recurrence. By adding the metabolic changes to the post-operative morphologic changes, combined positron emission tomography (PET) and computed tomography (CT) may offer clinically useful addition in operative bed evaluation. Results: The study included 30 patients, 17 males (56.6%) and 13 females (43.3%). Suspicious operative bed findings included pre-sacral soft tissue density noted in 20 patients (66%), anastomotic site mural thickening in five patients (16.6%), and post-operative loco-regional nodes in five patients (16.6%). Moreover, pre-sacral soft tissue focal avid uptake was noted in 17 patients (17/20, 85%), and no uptake noted in three patients (3/20, 15%). Anastomotic site mural thickening was seen in five patients with positive uptake noted in three patients (3/5, 60%), and no uptake seen in two patients (2/5, 40%). Loco-regional nodes were seen in five patients with positive uptake in five patients. The most accurate SUV max cut-off value among studied cases was 3.5. Confirmation of PET/CT results was done by histopathological assessment in ten patients (33.3%) and by follow up after 6 months in 20 patients (66.6%) with recurrence noted in 15 patients (75%) and normal post-operative findings noted in five patients (25%). Conclusion: PET/CT study is an effective tool for evaluation of suspicious colorectal oncologic operative bed findings noted in the routine CT studies. PET/CT fusion images affect the clinical management by guiding further procedures (surgery and radiation therapy).