Abstract
BackgroundLymph node metastasis of rectal neuroendocrine tumors (RNETs) predicts poor prognosis. However, the assessment of lymph node metastasis remains a challenge. It has been reported that 68Ga-DOTANOC and 18F-FDG PET-CT scans could be employed in the work-up of rectal neuroendocrine tumors (RNETs). This study aimed to assess both tracers’ ability to identify primary tumors and lymph node (LN) metastasis in RNETs.MethodsA total of 537 patients with RNETs were enrolled from January 2014 to January 2021. Both 68Ga-DOTANOC and 18F-FDG PET-CT scans were used to evaluate primary tumors and LN group metastasis. PET images were evaluated through visual and semiquantitative assessment. Receiver Operating Characteristics (ROC) curve analysis was used to investigate the performance of SUVmax of 68Ga-DOTANOC and 18F-FDG PET in predicting LN group metastasis.ResultsFifty-two patients with preoperative 68Ga-DOTANOC with 18F-FDG PET-CT scans underwent endoscopic biopsy or dissection of the primary tumor, while 11 patients underwent rectal surgery together with regional LN dissection. For primary tumors, 68Ga-DOTANOC had a sensitivity of 89.58% and a positive predictive value (PPV) of 95.56% through visual assessment, while 18F-FDG PET-CT showed 77.08% sensitivity and 97.37% PPV. For the prediction of LN group metastasis, 68Ga-DOTANOC PET-CT had 77.78% sensitivity and 91.67% specificity, while 18F-FDG PET-CT had 38.89% sensitivity and 100% specificity according to visual assessment. The area under the ROC curves (AUC) for 68Ga-DOTANOC PET/CT was 0.852 (95%CI:0.723-0.981) with an optimal SUVmax cut-off value of 2.25, while the AUC for 18F-FDG PET were 0.664 (95%CI:0.415-0.799) with an optimal SUVmax cut-off value of 1.05.ConclusionsThis study showed that 68Ga-DOTANOC PET-CT was a promising tool for detecting LN metastasis in RNETs with high sensitivity and specificity in visual assessment and semiquantitative assessment, which was better than 18F-FDG PET-CT.
Highlights
Neuroendocrine tumors (NETs) are considered rare tumors and constitute only 0.5% of all malignant conditions [1]
Visual Assessment Of the 52 patients included, 48 patients were pathologically diagnosed with NETs for the primary tumor, while the remaining 4 patients were determined to be negative by pathology for the primary tumor due to preoperative endoscopic dissection
The combination of 68GaDOTANOC and 18F-FDG PET-CT could increase the sensitivity to 93.75%
Summary
Neuroendocrine tumors (NETs) are considered rare tumors and constitute only 0.5% of all malignant conditions [1]. In 2010, the World Health Organization proposed that rectal neuroendocrine tumors (NETs) are classified as malignant tumors [4], and the 5-year survival rates for RNETs were 64.1% and 88% in Europe and North America, respectively [5,6,7]. Lymph node (LN) metastases were found in nearly 10% of cases [10]. Could predict LN metastasis [12], how to diagnose LN metastases accurately remains uncertain. Lymph node metastasis of rectal neuroendocrine tumors (RNETs) predicts poor prognosis. The assessment of lymph node metastasis remains a challenge. This study aimed to assess both tracers’ ability to identify primary tumors and lymph node (LN) metastasis in RNETs
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