Frequency of skeletal metastasis on 18F-fluorodeoxyglucose positron emission tomography/computed tomography with negative computed tomography at Institute of Nuclear Medicine and Oncology

Background: Skeletal metastasis (SM) with skeletal related events (SREs) occurs in up to 70% of breast cancer and more than 50% of malignant tumors. Whole-body 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) used to characterize the metabolic, anatomic, and morphologic status of suspected bone lesions. SMs are detected using multiple modalities; however, FDG PET/CT may offer a single investigation to detect SM combining the strength of functional imaging and radiological imaging simultaneously. Aims and Objectives: This study was to assess the frequency of SM on 18F-FDG PET/CT with negative CT at Institute of Nuclear Medicine and Oncology (INMOL). Materials and Methods: This cross-sectional study included a sample of total 50 patients with SM of known primary malignancies who underwent 18F-FDG PET/CT scan at INMOL Cancer Hospital, Lahore. Results: Of the 50 patients, we discovered the concordant findings between PET and CT as both PET+/CT+ in 38 patients (76%) whereas in 12 patients (24%) with PET+/CT- findings were discordant. CT was unable to detect SM in at least 12 patients. The maximum standardized uptake value (SUVmax) of SM in patients with negative CT found to be slightly higher as 5.2±4.1 (range: 2.5–7.8) than in patients with positive CT finding as 4.8±2.8 (range: 3.9–5.8) with P=0.76. P-value is insignificant this means that high SUV is not typical or conclusive evidence of metastasis. Conclusion: Despite limited data, this study has demonstrated high concordance between FDG PET and CT scan in detecting SM. Furthermore, the study has shown that 18F-FDG PET appears to have slightly better detection efficiency as compared to CT for identification of SM which is statistically insignificant. The study demonstrated that SUV is higher in PET and CT discordant cases; however, it does not provide conclusive information favoring diagnosis of SM.