Abstract: Objective:To investigate the clinical value of Fluorine18fluorodeoxyglucose ( ¹⁸F-FDG) PET/CT examination to predict the prognosis of patients after colorectal cancer operation.
Methods:The retrospective crosssectional 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 followup, (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 followup included tumor recurrence or progression and survival of patients. Tumorfree survival time was from postoperative day 1 to tumor recurrence or progression and death or end of followup. Overall survival time was from postoperative day 1 to death or end of followup. Measurement data with skewed distribution were represented as M (Qn) and M (range). The optimal cutoff point of tumorfree survival of maximum standardized uptake value (SUV max), mean standardized uptake value (SUV mean), 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 KaplanMeier method and Logrank 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 SUV max, SUV mean, 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 SUV max , SUV mean, 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 SUV max (11.83) and SUV mean(7.06) were used as the cutoff points due to smaller AUC of SUV max and SUV mean. 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 followup: among 80 patients, 13 underwent the radical resection of colorectal cancer and resection of liver metastasis and 67 underwent radical resection of colorectal cancer. Sixtytwo 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 followup, 29 patients had tumor recurrence or progression, and 19 patients were dead. The median tumorfree survival time, 1, 3 and 5year tumorfree 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 5year 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 tumorfree 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 tumorfree 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 tumorfree survival rate and overall survival rate in patients with colorectal cancer after curative resection, and it has certainly reference value for prognosis.