Clinical value of Fluorine-18-fluorodeoxyglucose PET/CT examination to predict the prognosis of patients after colorectal cancer operation

Abstract

Objective To investigate the clinical value of Fluorine-18-fluorodeoxyglucose (18F-FDG) PET/CT examination to predict the prognosis of patients after colorectal cancer operation. Methods The retrospective cross-sectional study was adopted. The clinicopathological data of 80 patients with colorectal cancer who were admitted to the First Hospital of Nanjing Medical University from March 2007 to October 2015 were collected. Eighty patients received first preoperative 18F-FDG PET/CT examination and underwent operations under decisions of patients and their families, and then adjuvant chemotherapy were performed according to the patients′ condition. Observation indicators included: (1) preoperative imaging examination, (2) situations of treatment and follow-up, (3) analysis of prognostic factors. The patients were followed up by outpatient examination and telephone interview once every 3 months within postoperative 1 year, once every half a year within postoperative 2 years and then once a year up to May 2016. The follow-up included tumor recurrence or progression and survival of patients. Tumor-free survival time was from postoperative day 1 to tumor recurrence or progression and death or end of follow-up. Overall survival time was from postoperative day 1 to death or end of follow-up. Measurement data with skewed distribution were represented as M (Qn) and M (range). The optimal cutoff point of tumor-free survival of maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), metabolism of volume (MTV) and total lesion of glycolysis (TLG) were investigated using the ROC curve analysis, and calculating area under the curve (AUC). The median was used as a cutoff point if there was smaller AUC. The Kaplan-Meier method and Log-rank test were respectively used for survival analysis and univariate analysis, and COX proportional hazards model for multivariate analysis. Results (1) Results of preoperative imaging examination: results of PET/CT in patients with colorectal cancer showed there were circumscribed thickening of bowel wall, intestinal cavity strictures, fuzzy fat space around the some lesions, enlarged lymph node and 18F-FDG uptake increased abnormally. The SUVmax, SUVmean, MTV and TLG of 80 patients were 11.83(4.26, 35.42), 7.06(2.38, 20.92), 20.47 cm3(1.29 cm3, 161.50 cm3) and 138.58(14.17, 857.89), respectively. ROC curve showed that the AUC of SUVmax , SUVmean, MTV and TLG were 0.453, 0.448, 0.815 and 0.749 [95% confidence interval (CI): 0.307-0.600, P>0.05; 0.303-0.594, P>0.05; 0.717- 0.913, P<0.05; 0.635- 0.863, P<0.05], respectively. The median SUVmax (11.83) and SUVmean(7.06) were used as the cutoff points due to smaller AUC of SUVmax and SUVmean. The cutoff point of MTV was 18.79 cm3 (sensitivity=86.2% and specificity=68.3%), and the cutoff point of TLG was 142.05 (sensitivity=75.9% and specificity=70.7%). (2) Situations of treatment and follow-up: among 80 patients, 13 underwent the radical resection of colorectal cancer and resection of liver metastasis and 67 underwent radical resection of colorectal cancer. Sixty-two patients received postoperative chemotherapy, including 45 with chemotherapy regimens of capecitabine and 17 with fluorouracil. Eighty patients were followed up for 41.8 months (range, 6.5-109.1 months ). During the follow-up, 29 patients had tumor recurrence or progression, and 19 patients were dead. The median tumor-free survival time, 1-, 3- and 5-year tumor-free survival rates in 80 patients were 19.5 months (range, 2.0-109.1 months), 73.7%, 36.3% and 18.8%, respectively. The median overall survival time, 1-, 3- and 5-year overall survival rates were 31.8 months (range, 3.3-109.1 months), 76.3%, 37.5% and 20.0%, respectively. (3) Analysis of prognostic factors: results of univariate analysis showed that tumor location, N staging, M staging, clinical staging, postoperative chemotherapy, MTV and TLG were relative factors affecting postoperative tumor-free survival rate (HR=3.469, 5.325, 5.295, 8.605, 2.630, 7.388, 5.155, 95% CI: 1.522-7.906, 2.256-12.568, 2.405-11.657, 2.969-24.937, 1.063-6.504, 2.550-21.403, 2.178-12.204, P<0.05). The tumor location, tumor differentiation, N staging, M staging, clinical staging, MTV and TLG were relative factors affecting postoperative overall survival rate (HR=2.697, 2.814, 3.083, 2.916, 4.193, 5.450, 4.876, 95% CI: 1.011-7.197, 1.121-7.062, 1.166-8.149, 1.140-7.454, 1.386-12.678, 1.581-18.786, 1.727-13.766, P<0.05). In multivariate analysis, stage Ⅲ-Ⅳ of clinical staging and TLG≥142.05 were independent risk factors affecting postoperative tumor-free survival rate (HR=9.879, 3.569, 95% CI: 1.854-22.836, 1.127-11.306, P<0.05). The stage M1, stage Ⅲ-Ⅳ of clinical staging and TLG≥142.05 were independent risk factors affecting postoperative overall survival rate (HR=4.522, 9.315, 10.120, 95% CI: 1.223-16.717, 1.338-24.864, 2.385-12.947, P<0.05). Conclusion TLG through 18F-FDG PET/CT examination is an independent prognostic factor affecting postoperative tumor-free survival rate and overall survival rate in patients with colorectal cancer after curative resection, and it has certainly reference value for prognosis. Key words: Colorectal neoplasms; Prognosis; Tomography, emission-computed; Tomography, X-ray computed; Deoxyglucose