The Value Of ¹⁸F-FDG PET/CT Imaging In The Monitoring Of Colorectal Cancer Recurrence

Objective:Analyzing the diagnostic efficacy of 18F-FDG PET/CT imaging and CEA level in colorectal cancer postoperative recurrence or metastasis; Analysizing the diagnosis efficiency difference of PET/CT、 PET、CT in different colorectal cancer recurrence;Analyzing and comparing the diagnostic efficacy of 18F-FDG PET/CT imaging in the normal CEA group and increased CEA group; Analyzing and comparing of the detectable rate of local recurrence 、 lung metastasis 、 liver metastasis、lymph node metastasis、peritoneal metastasis、bone metastasis and other parts metastasis(such as the brain, adrenal gland and spleen) in the normal CEA group and increased CEA group.Methods:We have selected colorectal cancer operation patients who underwent 18F-FDG PET/CT examination with suspected clinical symptoms, elevated levels CEA, or conventional imaging such as CT. According to whether elevated serum CEA levels before one week are divided into two groups: normal CEA group(CEA <5ng/ ml), increased CEA group(CEA ≥ 5ng / ml). We diagnostic recurrence or metastasis according to the pathological, colonoscopy, a variety of imaging examination or clinical follow up of at least 6 months.(1) Analyzing the diagnostic value(sensitivity, specificity, positive predictive value, negative predictive value and accuracy) of serum CEA and 18F-FDG PET/CT imaging for all patients with colorectal cancer recurrence or metastasis.(2) Analyzing the diagnosis efficiency diff--erence of PET/CT 、 PET 、 CT in colorectal cancer recurrence such as local recurrence, liver metastasis, lung metastasis.(3)And analyzing and comparing the diagnostic value(sensitivity, specificity, positive predictive value, negative predictive value and accuracy) of 18F-FDG PET/CT imaging for two group patients with colorectal cancer recurrence or metastasis.(4)According to18F-FDG PET/CT imaging of true positive, we have divided into local recurrence, liver metastasis, lung metasta--sis,lymph node metastasis, peritoneal metastasis, bone metastasis and the other part(such as the brain, adrenal gland and spleen) metastasis group. Analyzing and comparing the positive rate of 18F-FDG PET / CT imaging for different parts of metastatic or recurrent for two groups. Results:(1)The sensitivity, speci?city, positive predictive value(PPV), negative predictive value(NPV) and accuracy of the 18F-FDG-PET/CT were 99.5%(192/193), 89.6%(86/96), 95.0%(192/202), 98.9%(86/87), 96.2%(278/289). The sensitivity, speci?city, positive predictive value(PPV), negative predictive value(NPV) and accuracy of the serum CEA were 62.2%(120/193), 76.0%(73/96), 83.9%(120/143), 50%(73/146), 66.8%(193/289).(2) The diagnostic efficacy of PET/CT, PET, CT in the local recurrence of colorectal cancer have no significant difference; the sensitivity of PET/CT, PET in liver metastasis was higher than CT(P=0.068); the sensitivity and accuracy of PET/CT, CT in lung metastasis was higher than PET(P=0.005, P=0. 019).(3)The sensitivity, speci?city, positive predictive value(PPV), negative predictive value(NPV) and accuracy of the 18F-FDG-PET/CT in two groups were 98.6%(72/73), 90.4%(66/73),95.0%(192/202),91.1%(72/79), 94.5%(138/146) and100%(120/120), 87.0%(20/23), 97.6%(120/123),100%(20/20), 97.9%(140/143). The detection of 18F-FDG PET/CT in low group and elevated group showed no significant difference(P=0.378, P=0.636, P=0.085, P=1.0, P=0.133).(4) The incidence of local recurrence, liver metastases and abdominal lymph node metastasis detected with 18F-FDG PET/CT was significantly different in two groups(P=0.036, P<0.001, P=0.005); however, The incidence of lung metastasis, peritoneal metastasis, bone metastasis and other transfers detected with 18F-FDG PET/CT was not different between the two groups(P=0.177, P=0.264, P=0.103, P=0.120). Conclusions:(1) The sensitivity of PET/CT, PET in liver metastases of colorectal cancer was higher than CT; the sensitivity and accuracy of PET/CT, CT of colorectal cancer with lung metastasis are higher than PET; the diagnostic efficacy PET/CT, PET, CT in the local recurrence of colorectal cancer there was no significant difference.(2)The 18F-FDG PET/CT imaging has high sensitivity, speci?city, positive predictive value(PPV), negative predictive value(NPV) and accuracy for patients with colorectal cancer recurrence or metastasis. This shows that, the 18F-FDG PET/CT imaging has good sensitivity, speci?city for patients with colorectal cancer recurrence or metastasis when the CEA levels are normal.(3) The incidence of local recurrence, liver metastases and abdominal lymph node metastasis detected with 18F-FDG PET/CT was significantly different in two groups. If one patient after colorectal cancer surgery has elevated CEA levels, he should be alert to local recurrence, liver metastases and abdominal lymph node metastasis.(4)When 18F-FDG PET/CT imaging was underwent after the radiotherapy and chemotherapy in a short term(0~4 months), the imaging probably appear false positive results. The reason is mainly the inflammatory reaction after radiotherapy or chemotherapy result to the increase of the number of macrophages, lead to increased 18F-FDG uptake.(5) However, false negative probably appear in the special pathological type such as mucinous adenocarcinoma.The reason may be due to more mucus content in tumor tissue and less in tumor cells which lead to low uptake of 18F-FDG and PET imaging with no significant radioactivity. But this conclusion still need a large sample of support.