18F-FDG PET/CT in thoracic surgery or chest surgery is a fundamental molecular imaging tool for the diagnosis, staging, and monitoring of lung cancer, assisting in the preoperative evaluation of solitary pulmonary nodules (SPNs) by indicating malignancy through increased 18F-FDG uptake (Standardized Uptake Value or SUV). It helps determine the extent of the tumor, including lymph node infiltration, potentially reducing the need for unnecessary surgeries and improving accuracy compared to computed tomography. However, factors such as small lesion size, certain histological tumor types (such as adenocarcinoma in situ, lepidic-predominant adenocarcinomas, pulmonary carcinoids) can lead to false-negative results, while inflammatory processes can cause false-positive results.
Key Applications in Thoracic Surgery:
Diagnosis of Solitary Pulmonary Nodules (SPNs): 18F-FDG uptake in an SPN can indicate malignancy. SUV, a semi-quantitative measurement, helps differentiate benign from malignant lesions, with an SUVmax threshold of 2.5 commonly used.
Staging and Resectability Assessment: 18F-FDG PET/CT can detect metastases in lymph nodes and distant organs, which is critical for determining disease extent and surgical candidacy. The high accuracy of PET/CT in staging helps determine whether a patient is a candidate for curative resection, influencing the overall treatment plan.
Biopsy Guidance: PET/CT examination can guide biopsy location, potentially reducing the need for additional invasive procedures by identifying the most metabolically active, potentially malignant sites.
Prevention of Unnecessary Surgery: By identifying advanced or metastatic disease not apparent on computed tomography, PET/CT can prevent patients from undergoing unnecessary and potentially harmful surgeries.
Treatment Planning: It helps surgeons select the appropriate surgical approach. It evaluates the effectiveness of chemotherapy or radiotherapy by detecting changes in metabolic activity before anatomical changes become visible.
Advantages Over Conventional Imaging:
Functional Versus Morphological Imaging: While computed tomography provides detailed anatomical information, PET/CT detects increased metabolic activity, which is a hallmark of many cancers, providing functional information that complements anatomical details.
Improved Accuracy: Studies show significantly higher accuracy, sensitivity, and specificity in staging and detecting malignant lymph nodes when PET/CT is used compared to computed tomography.
Reduced False-Negative Results: PET/CT has a high negative predictive value, meaning a negative PET/CT scan can be relied upon to a greater extent than a negative CT scan for excluding mediastinal lymph node infiltration.
Limitations:
High Sensitivity but Variable Specificity: While excellent at detecting malignancy, PET/CT can sometimes be positive in cases of benign conditions such as inflammation or infection.
Need for Histopathological Confirmation: A positive PET/CT finding, especially in mediastinal lymph nodes, generally requires confirmation with histopathological biopsy to ensure staging accuracy.
Incomplete Evaluation: PET/CT examination cannot be considered absolutely accurate for detecting all possible metastases, and a surgeon must always consider the possibility of undetected or occult disease when making treatment decisions.