The role of PET/CT in the differential diagnosis of lung lesions

Abstract

Background. Lung cancer is a leading cause of cancer morbidity and mortality. The lungs are a frequent target for metastasis from malignant tumors in other locations, necessitating timely and accurate differential diagnosis. Positron emission tomography/computed tomography (PET/CT) with 18F-fluorodeoxyglucose (18F-FDG) has proven highly informative, but its accuracy in certain clinical scenarios remains controversial. Study Objective. To evaluate the informative value of 18F-FDG PET/CT in diagnosing solitary lung lesions and differentiating them into primary, metastatic, and benign. Materials and Methods. Data from 32 patients with newly diagnosed focal lung lesions (58.3% men, 41.7% women, ages 22–82 years, median 59 years) were analyzed. All patients underwent whole-body PET/CT with 18F-FDG, followed by surgery with morphological verification. Histology results revealed lung cancer in 17 patients (53.1%), metastatic lesions in 11 (34.4%), and benign changes in 4 (12.5%). The intensity of radiopharmaceutical uptake was assessed by SUVmax; ROC analysis was performed. Results and discussion. The median SUVmax in the overall group was 6.0 (IQR 3.9–8.4); for lung cancer, it was 7.0 (IQR 5.8–10.9), and for metastases, it was 4.3 (IQR 2.5–7.1). The optimal SUVmax cutoff value for detecting malignant neoplasms was 5.4, providing a balance between sensitivity and specificity. PET/CT tended to underestimate the size of lesions up to 40 mm and overestimate those larger. A linear model of 5.862 + 0.817×x (where x is the PET/CT size) predicted the true size with an accuracy of 84.5%, with an error margin of ±50%. Conclusion. PET/CT with 18F-FDG is a highly informative method for the differential diagnosis of solitary lung lesions. A SUVmax threshold of ≥ 5.4 improves the accuracy of detecting malignant processes, and the use of a corrective linear model improves size estimation, which is important for staging and treatment planning.

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