| ObjectiveThe recurrence and metastasis of colorectal cancer post-operation are common, and they are also the major causes of the mortality. It is of great significance for making the right therapeutic management decision to estimate whether there are recurrence and metastasis or not, and to evaluate the extent of the patients with the known diagnosis. At present,the clinical diagnosis information is mainly from the detailed physical examination,serum CEA level,colonoscopy and the conventional imaging modalities; however there is some limit in the diagnostic sensitivity and specialty. Some researches have shown that 18F-FDG PET has some important efficacy in the early diagnosis of the recurrent and metastatic colorectal cancer, in the differentiation between the postoperative scar and the tumor recurrence, in the pre-surgical assessment; anyway it is also a useful adjunct to the conventional modalities. We report our experience with the use of the whole-body 18F-FDG PET/CT in 75 patients with suspected recurrent and metastatic colorectal cancer, to investigate the clinical value of 18F-FDG PET/CT for investigating elevated serum CEA in post operative patients with colorectal cancer.Materials and Methods75 patients with colorectal cancer post-operation were examined with 18F-FDG PET/CT,42 are males,33 are females, age range 37-82 years,mean age 60.3 years. Based on the serum CEA level, there were two groups. Group1,35 patients whose serum CEA level was elevated. Group2,40 patients whose serum CEA level was in normal range. All patients were examined with 18F-FDG PET/CT. Scan from the top of the skull through the mid-thigh. Low-dose CT scanning was performed first, PET scanning was performed immediately after acquisition of the CT images, and the CT data were used for attenuation correction. PET images were reconstructed and fused with CT images, then displayed in three orthogonal projections. Images were interpreted by two experienced imaging physicians at the workstation. All of the 18F-FDG uptakes in PET images were evaluated visually and semi-quantitatively using the standard uptake value (SUV), PET images were read in conjunction with relevant the CT and the fused images. At last, making the diagnosis about whether there was recurrence and metastasis or not for each patient, and reporting the position and the extent. The measurement of serum CEA and the conventional imaging examinations were performed before the PET/CT examinations. The final diagnosis were confirmed by histopathology or by clinical course and conventional imaging modalities follow-up whenever possible, the therapeutic decisions making were based on the surgeons'advice. Comparing the results of PET/CT with the CEA levels, the conventional imaging examinations and the final diagnosis, calculating the sensitivity, the specificity, the accuracy, the positive predictive value and the negative predictive value of PET/CT. Investigate the clinical value of 18F-FDG PET/CT for investigating elevated serum CEA in post operative patients with colorectal cancer.ResultsThe results of 18F-FDG PET/CT examinations of the 75 patienis:35 were diagnosis as no recurrence or metastasis.17 were diagnosis as local recurrence and 23 were diagnosis as extensive metastasis. The final diagnosis of the 75 patienis,37 had no recurrence or metastasis, and after the clinical follow-up for more than 12 months, the patients still survived without disease.16 had local recurrence or metastasis and 22 had extensive lesions, which were confirmed by histopathology or by conventional imaging modalities follow-up. Comparing with the final diagnosis, PET/CT yielded a correct diagnosis in 69 out of 75 patients,4 were false-positive,2 was false-negative.The accuracy, sensitivity, specificity, PPV and NPV of PET/CT in detecting of recurrence or metastasis was 92.0%,94.7%,89.2%,90.0% and94.3%,respectively.Coneclusion18F-FDG PET/CT has some promising clinical value in the patients with colorectal post-operation.18F-FDG PET/CT is capable identifying recurrence and metastasis in the patients with unexplained rising CEA in the postoperative surveillance of colorectal cancer, but with equal findings on conventional diagnostic modalities. Making the differential diagnosis of the unspecific findings, which were on the conventional imaging modalities. Determining the extent of the recurrence and metastasis, helping the physicians implement the appropriate therapy. However, there are still false-positive and false-negative diagnosis, combining the clinical information and the low-dose CT examination can reduce the false diagnosis to the best of our abilities. Serum CEA, although the judge in the early postoperative recurrence of colorectal cancer, the transfer also has important clinical value, but also has some inaccuracies, if their combination is able to significantly improve patients with colorectal cancer recurrence and metastasis after diagnostic accuracy. |
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