The value of FDG-PET in diagnosing peritoneal seeding of colorectal cancer

Peritoneal seeding of colon cancer cells is a common cause of morbidity and eventual mortality with recurrent disease. This study evaluated the role of F -18 FDG PET in detecting peritoneal seeding in colorectal carcinoma (CRC and to identify characteristic patterns of abdominal F-18 FDG uptake. We reviewed the FDG PET and CT images and clinical charts of 49 patients with peritoneal seeding and 22 cancer patients without peritoneal seeding. We also assessed FDG PET scans from 20 healthy volunteers as a baseline study. The maximum standardised uptake values (SUVmax) over peritoneal lesions in cancer patients and over the area of most intense intestinal uptake in healthy volunteers and cancer patients without peritoneal carcinomatosis were measured. The result were correlated with either biopsy or ascitic aspirate. The characteristics of FDG uptake were evaluated: overall pattern (focal or diffuse), heterogeneity (yes or none), intensity (low, or equal, faint to moderate, intense). The sensitivity and positive predictive value (PPV) of FDG PET were superior to CT for the detection of peritoneal lesions (sensitivity: 71.4% vs 57.1%, specificity: 72.7% vs 54.5%: PPV: 85.4% vs 73.7%, NPV: 53.3 % vs 36.4% ). The FDG uptake in patients with peritoneal carcinomatosis was divided into nodular(14), diffuse (23) and mixed pattern (12). An SUVmax threshold of 5.2 produced a diagnostic accuracy of FDG PET of 78%. The additional information provided by FDG PET allowed a more accurate diagnosis in 12 patients (24 %), and led to alteration of the therapeutic strategy in 6 (12.2%) of the enrolled patients (n=49) with peritoneal seeding. FDG-PET was more sensitive than CT for the detection of peritoneal seeding in CRC, and altered patient management. Thus, the application of PET may be beneficial to the management of peritoneal seeding in patient with CRC