A Comparison Between 18F-FDG PET/CT and Classical Physical Examination Package for Cancer Screening in Asymptomatic Chinese Patients
Cancer remains the leading cause of death in China, and with rapid economic development, the use of 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for cancer screening in asymptomatic patients has gained popularity. PET/CT is a molecular imaging technology that uses a specific tracer to localize and quantify diseases at a molecular level. However, the utility of PET/CT for cancer screening remains controversial. In contrast, a classical physical examination protocol has been optimized based on past clinical experience and is widely used in clinical practice. This study aims to compare the diagnostic performance of 18F-FDG PET/CT and the classical physical examination package for cancer screening in asymptomatic Chinese patients.
The study retrospectively reviewed asymptomatic patients who voluntarily chose to undergo FDG PET/CT examination at the Department of Health Medicine of the Chinese PLA General Hospital between January 1, 2015, and December 31, 2017. Patients with a history of malignant tumors or incomplete clinical data were excluded. The study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of the Chinese PLA General Hospital. A total of 5934 individuals who underwent FDG PET/CT examination were reviewed, and 2843 agreed to undergo endoscopic examinations. After excluding 52 patients due to inadequate laboratory tests and imaging examinations, 2791 individuals were included in the analysis.
The FDG PET/CT examinations were performed using a Siemens Biograph 64 HD machine. Patients were required to fast for at least 4 hours before imaging, and their serum glucose levels were maintained below 6.5 mmol/L. A dose of 4.44 MBq/kg of 18F-FDG was administered intravenously, and whole-body PET scanning was performed 45 to 60 minutes after injection. The median effective dose from 18F-FDG PET was 3.69 mSv, while that from low-dose CT was 4.93 mSv, resulting in a median total effective dose of 8.85 mSv. The images were interpreted by two nuclear medicine physicians, and clinical data, including general information, past history, personal history, family history of cancer, physical examination, laboratory tests, imaging examinations, endoscopic examinations, and FDG PET/CT results, were collected retrospectively.
In the cancer screening program, 64 (2.29%) of the 2791 individuals were found to have malignant tumors, with a mean age of 61.72 ± 17.12 years (range: 28–91 years). The detection rate of malignancy increased with age, from 1.11% in individuals younger than 50 years to 3.57% in those older than 50 (P < 0.05). Among the 64 cancer cases, 59 were detected by the classical physical examination package, which included 19 cases of colorectal cancer, 16 cases of lung cancer, 9 cases of stomach cancer, 3 cases of hepatocellular carcinoma (HC), 4 cases of thyroid cancer, 2 cases of esophagus cancer, 1 case of renal cancer, 2 cases of gall bladder cancer, 1 case of pancreatic cancer, 1 case of bladder cancer, and 1 case of breast cancer.
In the FDG PET/CT screening, 90 subjects showed abnormal FDG uptake or malignant changes, of which 52 were confirmed to have cancer based on pathological reports. These included 13 cases of colorectal cancer, 17 cases of lung cancer, 9 cases of stomach cancer, 2 cases of HC, 4 cases of thyroid cancer, 1 case of esophagus cancer, 1 case of renal cancer, 2 cases of gall bladder cancer, 2 cases of pancreatic cancer, and 1 case of breast cancer. The detection rate of FDG PET/CT in cancer screening was 1.86% (52/2791). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of FDG PET/CT were 81.25%, 98.61%, 57.78%, and 99.56%, respectively. There were 38 false-positive lesions in FDG PET/CT, including 16 cases in the thyroid, 5 in the stomach, 6 in the colon, 2 in the prostate, 2 in the gallbladder, 1 in the liver, 1 in the breast, 2 in the lung, 1 in the pancreas, 1 in the shoulder joint, and 1 in the gluteus maximus. These lesions were confirmed as benign by histological methods. Additionally, there were 12 false-negative cases, including 2 cases of lung cancer, 2 cases of colorectal cancer, and 1 case each of thyroid cancer, HC, esophagus cancer, and bladder cancer. These cases showed no abnormal focal FDG accumulation in PET/CT but were later diagnosed with cancer through other screening methods, such as ultrasonography, magnetic resonance imaging, laboratory tests, and endoscopic examinations.
In the classical physical examination package, 61 subjects were suspected of having malignant lesions, of which 59 were confirmed to be truly positive. The detection rate of the classical physical examination package in cancer screening was 2.11% (59/2791). The sensitivity, specificity, PPV, and NPV of the classical physical examination package were 92.19%, 99.93%, 96.72%, and 99.82%, respectively. There were only 2 false-positive lesions, both confined to the lungs, and 5 false-negative cases, including 3 cases of lung cancer and 1 case each of thyroid cancer and pancreatic cancer.
To assess the diagnostic power of the two cancer-screening protocols, a receiver operating characteristic (ROC) curve analysis was performed. The area under the ROC curve (AUC) for FDG PET/CT was 0.898 (95% confidence interval [CI]: 0.840–0.955), while that for the classical physical examination package was 0.952 (95% CI: 0.909–0.994). The classical physical examination package showed significantly higher diagnostic accuracy compared to FDG PET/CT (P < 0.001).
The study concluded that while whole-body FDG PET/CT demonstrated good performance in cancer screening, the classical physical examination package exhibited higher sensitivity, specificity, PPV, and NPV. The false-positive findings in FDG PET/CT were primarily due to active inflammatory lesions, small size lesions, benign tumors, and aberrant physiologic FDG uptake in normal organs. Distinguishing gastrointestinal cancers and thyroid incidentalomas posed significant challenges for FDG PET/CT, as there is no safe SUVmax cutoff to discriminate benign from malignant thyroid lesions, and only one-third of focal uptakes are malignant. Additionally, small lung tumors, such as ground-glass nodules (GGN), were limitations for both FDG PET/CT and the classical physical examination package.
The study had several limitations. First, it was a single-center retrospective study, and most subjects were economically sound, which may limit the generalizability of the results to the broader population. Second, the study included few subjects older than 80 years or younger than 30 years, potentially introducing bias. Therefore, multi-center studies are needed to confirm these findings in populations with diverse economic backgrounds.
In conclusion, the classical physical examination package may be a more effective modality for cancer screening in asymptomatic patients compared to FDG PET/CT. FDG PET/CT is more suitable for patients with positive or suspected results from the classical physical examination, particularly in high-risk groups. Further research is needed to validate these findings and explore the optimal use of both screening methods in different populations.
doi.org/10.1097/CM9.0000000000001376
Was this helpful?
0 / 0