Disease-specific Factors Influenced Lymph Node Metastasis of Diagnostic Accuracy of 18F Fluorodeoxyglucose Positron Emission Tomography/computed Tomography in Colorectal Cancer : a Single-center Study

Background: The usefulness of preoperative lymph node metastasis diagnosis by 18F fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) in colorectal cancer management has been reported, but inadequate diagnostic accuracy precludes routine preoperative application. Therefore, the purpose of this study was to examine the factors influencing the diagnostic accuracy of lymph node metastasis by PET/CT in patients with colorectal cancer.Methods: We retrospectively identified 864 patients who underwent preoperative PET/CT and colorectal cancer resection at Shizuoka General hospital from January 2017 to December 2019. We examined factors influencing the diagnostic accuracy of PET/CT to detect lymph node metastasis generally and lymph node metastasis for each TNM stage according to the UICC-TNM 8th edition.Results: The overall sensitivity and specificity of PET/CT to detect lymph node metastasis in patients with colorectal cancer were 61.2% and 75.9%, respectively. Distant lymph node metastasis was diagnosed more accurately than regional lymph node metastasis. “T category” (T1/T2 vs. T3/T4) was an independent factor affecting the lymph node metastasis diagnostic capability among patients negative for lymph node metastasis [p<0.01; odds ratio 2.20; 95% CI 1.28-3.84], while among patients positive for lymph node metastasis, “Tumor diameter” was significantly associated with the lymph node metastasis diagnostic capability on univariate analysis [p=0.02]. The sensitivity and specificity of PET/CT for Stage I (T1/T2, N0) were 82.5% and 84.6%, respectively. For more advanced tumors, the diagnostic ability to detect lymph node metastasis decreased. Conclusions: Disease-specific factors such as T category and tumor diameter significantly impacted on LN metastasis diagnosis by PET/CT in patients with colorectal cancer. We recommended the preoperative application of PET/CT only for the diagnosis of distant lymph node metastasis.

High false-positive rate of fluorodeoxyglucose positron emission tomography to detect lymph node metastasis in microinvasive cervical cancer after conization

We aimed to estimate the positive predictive value of fluorodeoxyglucose positron emission tomography (FDG PET) to detect lymph node metastasis in patients with microinvasive cervical cancer who recently underwent conization. We retrospectively collected data of patients fulfilling the following criteria: 1) cervical cancer stage 1A1 (by FIGO staging revised in 1994) without invasion of the lymphovascular space diagnosed by conization from September 2008 to July 2018, 2) FDG PET within 3 months after diagnosis, 3) lymph node metastasis suspected by FDG PET, and 4) histologic confirmation or follow-up imaging study for suspected lymph node metastasis. Lymph node metastasis was suspected in 31 regions in 18 patients; however, no true metastasis was found. In conclusion, lymph node metastasis suspected by FDG PET in microinvasive cervical cancer after conization might be false positive. Lymph node dissection should not be performed for such patients.

Affinity of Indocyanine Green in the Detection of Colorectal Peritoneal Carcinomatosis

Indocyanine green (ICG) is increasingly being used in digestive oncology. In colorectal cancer, ICG can be used to detect lymph node metastasis and hepatic metastasis on the surface of the liver. In peritoneal carcinomatosis, it was previously suspected that the diffusion of ICG in the tumor mass was due to the enhanced permeability and retention effect; however, this phenomenon has not been clearly demonstrated. Using bevacizumab, an antibody directed against vascular endothelial growth factor that consequently inhibits neoangiogenesis, we sought to confirm the mode of ICG diffusion. We compared the fluorescence of peritoneal carcinomatosis nodules from patients who had previously received bevacizumab during their oncologic treatment with those who did not receive this therapy. The sensitivity of the carcinomatosis nodule fluorescence was higher in the patients who did not receive bevacizumab compared with those who received the drug (76.3% and 65.0%, respectively). The rate of false-negative results was higher in the bevacizumab group than in the group that did not receive the drug (53.8% and 42.9%, respectively). Using bevacizumab, we demonstrate that the enhanced permeability and retention effect causes ICG accumulation in peritoneal carcinomatosis resulting from colorectal cancer.