Detection of Liver Lesions in Colorectal Cancer Patients Using (18)F-FDG PET/CT Dual-Time-Point Scan Imaging

SIMPLE SUMMARY: Fluorine-18-fluorodeoxyglucose positron emission computed tomography/computed tomography ((18)F-FDG PET/CT) imaging is crucial for staging, restaging, and therapeutic response assessment in colorectal cancer (CRC) patients. However, (18)F-FDG is not specific for malignant lesions. Dual-time-point imaging has emerged as a promising tool to address this limitation. Our findings indicate that delayed PET/CT images significantly increased both sensitivity (87.7% vs. 100%) and specificity (94% vs. 91%) compared to standard early images. Therefore, our study demonstrated the added value of dual-time-point scans with little extra cost and radiation exposure. ABSTRACT: Objective: The aim of this study was to evaluate the diagnostic performance of dual-time-point fluorine-18-fluorodeoxyglucose positron emission computed tomography/computed tomography ((18)F-FDG PET/CT) compared to conventional early imaging for detecting colorectal liver metastases (CRLM) in colorectal cancer (CRC) patients. Methods: One hundred twenty-four consecutive CRC patients underwent dual-time-point imaging scans on a retrospective basis. Histopathological confirmation and/or clinical follow-up were accepted as the gold standard. Standard uptake values (SUV), signal-to-noise ratio (SNR), retention index (RI), tumor-to-normal liver ratio (TNR), and lesion sizes were measured for early and delayed PET scans. The diagnostic performance of early and delayed images was calculated on a per-patient basis and compared using McNemar’s test. Results: Among the 124 patients, 57 (46%) had CRLM, 6 (4.8%) had benign lesions, and 61 (49.2%) had no concerning lesions detected. Smaller CRLM lesions (<5 cm(3)) showed significantly higher uptake in the delayed scans relative to early imaging (p < 0.001). The SUV and TNR increased significantly in delayed imaging of all metastatic lesions (p < 0.001). The retention index of all CRLM was high (40.8%), especially for small lesions (54.8%). A total of 177 lesions in delayed images and 124 in standard early images were identified. In a per-patient analysis, delayed imaging had significantly higher sensitivity (100% vs. 87.7%) and specificity (91.0% vs. 94.0%) compared to early imaging (p-value = 0.04). Conclusions: The detection of liver lesions using dual-time-point PET/CT scan improves the sensitivity and specificity for the detection of colorectal liver metastasis.