Accuracy of F-18 FDG PET/CT with optimal cut-offs of maximum standardized uptake value according to size for diagnosis of regional lymph node metastasis in patients with rectal cancer

Abstract

BackgroundThe low sensitivity of F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for the evaluation of metastatic lymph nodes (LNs) is mainly due to the partial volume effect in patients with rectal cancer. This retrospective study evaluated the diagnostic accuracy of F-18 FDG PET/CT with optimal cut-off values of the maximum standardized uptake value (SUVmax), according to LN size, for the evaluation of regional LN in rectal cancer patients.MethodsThis study included 176 patients with rectal cancer who underwent F-18 FDG PET/CT for initial staging. Patients were classified based on the long-axis diameter of the regional LN on CT images as small (≤ 7 mm; n = 118) and large (> 7 mm; n = 58) LN groups. The optimal cut-off value of SUVmax was determined for each group, using receiver operating characteristic curve analysis. Areas under the curve (AUC) were compared by C-statistics using two methods: the cut-off value of SUVmax optimized according to LN size, and a fixed SUVmax cut-off value of 2.5.ResultsThe optimal cut-off values of SUVmax for the small and large LN groups were 1.1, and 2.1, respectively. The sensitivity, specificity, and accuracy of F-18 FDG PET/CT using the optimal cut-off values were 90.6, 70.9, and 76.3% in the small LN group, and 68.6, 78.3, and 72.4% in the large LN group. The sensitivity, specificity, and accuracy of F-18 FDG PET/CT using the fixed cut-off value were 18.8, 100, and 78.0% in the small LN group, and 51.4, 87.0, and 65.5% in the large LN group. The AUC was significantly higher using the optimal cut-off values than the fixed cut-off value (0.808 vs. 0.594, p = 0.005) in the small LN group, but not in the large LN group (0.734 vs. 0.692, p = 0.429).ConclusionsApplication of the lower cut-off value of SUVmax improves the diagnostic performance of F-18 FDG PET/CT for the evaluation of small regional LNs in patients with rectal cancer.Electronic supplementary materialThe online version of this article (10.1186/s40644-018-0165-5) contains supplementary material, which is available to authorized users.

Contrast‑enhanced CT imaging for the assessment of lymph node status in patients with colorectal cancer

“…However, the use of MRI to assess LN status may lead to overdiagnosis (36), and therefore may be an unreliable tool (40,41). The performance of positron emission tomography combined with fluorine-18 fluorodeoxyglucose for predicting LN+ may also be insufficient to assess LN status (42,43).…”

Is 18F-FDG PET/CT an Accurate Way to Detect Lymph Node Metastasis in Colorectal Cancer: A Systematic Review and Meta-Analysis

“…18 F-FDG PET/CT demonstrates a low sensitivity and high specificity for detecting the metastasis of LNs in patients with newly diagnosed CRC. Also, 18 F-FDG PET/CT is only useful for the confirmation of LN metastasis (when positive) in patients with CRC.…”

“…e present meta-analysis provided a comprehensive overview of the literature, highlighted the causes of heterogeneity, and explored the clinical application of 18 F-FDG PET/CT function in staging in this neoplasm in previous articles. 18 F-FDG PET/CT was widely used for staging in a large number of oncologic diseases. For rectal cancer, this is used for staging tumors and LN, which may affect treatment planning.…”

“…(ii) PET/ CT imaging has pitfalls due to high FDG uptake by physiological causes, increased FDG uptake due to inflammation, benign thyroid nodules, recent chemoradiotherapy, unilateral cranial nerve palsy, and recent surgery. 18 F-FDG PET/ CT is only useful for the confirmation of LN metastasis (when positive) in patients with colorectal cancer. (iii) Prospective designed studies, studies with sample size < 100, and those that used SUV max cut-off value ≤ 2.5demonstrated the best accuracy.…”

“…e low sensitivity of F-18 FDG PET/CT in the evaluation of metastatic LNs is mainly due to the partial volume effect that spills out the radioactivity into the background of small lesions <10 mm in size, which makes the actual standardized uptake value (SUV) insignificant. [17][18][19].…”