Value Of ¹⁸F-FDG PET-CT Imaging In Clinical Diagnosis Of Peritoneal Metastases

Objective: To assess the performance of ¹⁸F-FDG PET-CT examination in the diagnosis and evaluation of the extent of peritoneal carcinomatosis?PC?; analyzing the typical characteristics of PC on ¹⁸F-FDG PET-CT imaging.Methods:A retrospective analysis was conducted on 53 patients with suspected PC from the Tianjin Medical University Cancer Institute and Hospital from 2011 to 2015. We analyzed ¹⁸F-FDG PET-CT scans and histopathological examinations which were taken as a golden standard in all cases, and evaluated the extent of the PC with ¹⁸F-FDG PET-CT PCI and confirmed PCI based on Sugarbaker's peritoneal carcinomatosis index?PCI? separately.?1? By lesion basis, analyzing the diagnostic value?sensitivity, specificity, positive predictive value?PPV?, negative predictive value?NPV? and accuracy? of ¹⁸F-FDG PET-CT scan for all sites of PC as well as smaller than 0.5cm, analyzing the distribution proportion of different sizes of PC.?2? By lesion basis, analyzing the diagnostic value of ¹⁸F-FDG PET-CT scan for PC happened in different parts of peritoneum, analyzing the regional difference of PC from different tumors.?3? By patient basis, Pearson's correlation coefficient and linear regression was calculated to describe the strength of linear relationship between ¹⁸F-FDG PET-CT PCI and confirmed PCI, and the predictive value for intraoperative tumor load of ¹⁸F-FDG PET-CT PCI; A Mc Nemar test was used to assese the diagnostic accuracy of ¹⁸F-FDG PET-CT PCI extent of carcinomatosis.?4? Analyzing and summaring the typical characteristics of PC on ¹⁸F-FDG PET-CT imaging depending on ture positives.?5? Analyzing the results of false positive and false negative.Results:?1? By lesion basis, the sensitivity, specificity, PPV, NPV and accuracy of ¹⁸F-FDG PET-CT scan for all sites of PC were 84.5%?90.8%?96.1%?65.3%?86.2, and for those smaller than 0.5cm were 61.0%?58.4%?70.1%?48.4%?60.0%; the distribution proportion of PC sizes ?0.5cm?0.5cm⁵cm??5cm were 29.8%?43.9%?26.2%.?2? By lesion basis, the sites of disease most frequently involved were the greater omentum?18.4%?, the mesentery?15.0%?, the small intestinal?13.1%?, and the pelvic?10.7%?, the rest consisted 42.8%, the sensitivity of ¹⁸F-FDG PET-CT scan for different regions of PC were the mesentery?67.7%?, the small intestinal?79.6%?, the pelvic?84.1%?, and the greater omentum?85.5%?, all be inferior to the other parts. The most common regions involved were the pelvis?75%?, the caecum?71%?, the proctosigmoid?67%?, the distal ileum?69%?, and the greater omentum?65%? in colorectal carcinoma, and the subdiaphragmatic space?84%?, the pouch of Douglas?79%?, the right and left paracolic gutters?77%?, the area above the mesosigmoid tract?71%?, and the ileocecal region?65%? in ovarian cancer, the greater omentum?89%?, the subdiaphragmatic space?72%?, the splenic capsule?70%?, the pelvic?70%?, and the extrastomach ligment?65%? in gastric carcinoma.?3? A strong and statistically significant correlation was found between the results of ¹⁸F-FDG PET-CT PCI and confirmed PCI in the Pearson's correlation analysis?r=0.945,P<0.05?; ¹⁸F-FDG PET-CT PCI yielded a good result?r2=0.894,P<0.05? for the prediction of intraoperative tumor load, evaluated by linear regression analysis; the diagnostic accuracy of ¹⁸F-FDG PET-CT PCI extent of carcinomatosis is 90.6%?chi-square value=8.600, P<0.05, compared the results of the two?.?4? By patient basis, the mean maximum standardized uptake values?SUVmax?of all cases was 9.3�3.9?3.9¹0.7?, of which mucinous tumors' was 5.6�1.9?2.7⁸.6?; the typical signs of PC on ¹⁸F-FDG PET-CT imaging were: the parietal peritoneum irregular thickening?67.6%?, or regular, smooth nodular?11.8%?; the greater\lesser omentum appears numerous miliary nodules?14.7%?, or nodular, omental cake of variable thickness?50.0%?; the mesentery appears infiltration, stranding thickening?67.6%?; small-bowel wall thickening or distortion, adhesion to surrounding tissues?44.1%?; the gallbladder forssa, the extrastomach ligment, the ovary, and the bladder wall et al organs involved with surface irregular thickening, or nodular?35.3%?; ascites was found in 31/32 of cases, accuracy was 96.9%.?5? False-positives were found in two cases, among which one resulted from the inflammatory reaction after radiotherapy or chemotherapy in a short term, the other one was resulted of inflammatory disease of normal tissue; false positives were found in five cases, among which two were resulted from small lesions? one is mucinous adenocarcinoma?,no abnormality was seen on ¹⁸F-FDG PET-CT imaging, one shown as small bowel wall slightly thickening, with uptake of ¹⁸F-FDG, diagnosed with physiological change, one shown a smooth nodule of pelvic diagnosed with inflamed lymph node, and the other mucous adenocarcinoma in ovarian cancer diagnosed with benign lesions.Conclusions:?1? The ¹⁸F-FDG PET-CT scan has high diagnostic value for patients with PC;?2? The most frequently involved sites of PC?greater omentum, the mesentery, the small intestinal, and the pelvic? were those need extra attention, involved regions were different between different tumours including colorectal carcinoma, ovarian cancer, and gastric carcinoma, respectively.?3? ¹⁸F-FDG PET-CT PCI showed a significant correlation and predicting value for intraoperative tumor load when used as preoperative examination of PC.?4? The typical signs of PC on ¹⁸F-FDG PET-CT imaging were parietal\visceral peritoneum's abnormal morphological changes, with utake of ¹⁸F-FDG varying different degrees.?5? Small lesions,physiological uptake of ¹⁸F-FDG, inflammatory diseases, special pathological types such as mucinous adenocarcinoma, the inflammatory reaction after radiotherapy or chemotherapy in a short term would result false positives or false negatives, indicated consideration of all factors should be taken.