Malignancies of Lower Gastroenterological Tract
18F-FDG PET/CT has a limited use in detecting primary colorectal cancer. False-negative results may be present in small tumors or in mucinous lesions [1–3], while false positives have been observed in patients with Inflammatory Bowel Diseases (IBD) or previous diagnostic polypectomy . With 18F FDG-PET being more accurate than CT in detecting lymph node metastases, conversely CT is more sensitive for liver metastases. Because of the high incidence of disease recurrence (30–40%), an integrated PET/CT examination, also using contrast media, may be requested in selected patients with a high probability of distant secondarisms. Furthermore, because FDG’s uptake is expression of tumor aggressiveness, PET/CT pre-therapeutic utilization is also suggested as a prognostic tool; similarly, it is important to acquire a basal study, when it is supposed to utilize FDG to evaluate therapeutic response in follow-up . Nevertheless, in the preoperative initial staging of disease, 18F-FDG PET/CT is considered potentially useful, although not yet sufficiently validated as first-line procedure .
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