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그림) Flowchart for differential diagnosis of single-bone FDG lesions in 118 newly diagnosed NSCLC patients. Using this method, PET/CT features correctly recognized 25 metastatic and 56 benign bone lesions. Only 37 bone lesions remained that required further evaluation for differentiation

Abstract
OBJECTIVES:
We investigated the capacity of fluorodeoxyglucose (FDG) PET/CT features for stratifying probability of metastasis for single-bone FDG lesions in non-small-cell lung cancer (NSCLC).

METHODS:
Subjects were 118 newly diagnosed NSCLC patients with a solitary bone FDG lesion and no evidence of other distant metastasis based on PET/CT, brain MRI, and contrast-enhanced chest CT. Bone lesion SUVmax and CT findings, primary tumor SUVmax, clinical T stage, and N stage were analyzed.

RESULTS:
The bone lesions were determined by biopsy, characteristic MRI findings and clinical follow-up to be metastatic in 33 (28.0%) and benign in 85 cases (72.0%). A cutoff bone SUVmax of 4.3 showed good diagnostic performance (81.8% sensitivity, 84.7% specificity, and 83.9% accuracy), but there was considerable overlap. Bone lesion PET/CT features of SUVmax ≤ 2, osteosclerotic rim or fracture correctly diagnosed 20/20 benign, while SUVmax > 10, soft-tissue mass or bone destruction correctly diagnosed 18/18 metastatic cases. In the remaining 80 cases, bone features of SUVmax > 4.3 and osteolytic change, and lung tumor features of SUVmax > 6.4, ≥ T2 stage (n = 70), and ≥ N1 stage (n = 43) favored metastasis. The presence of one or less of these features correctly diagnosed 38/38 benign, while the presence of four or more features correctly diagnosed 5/5 metastatic cases. The 37 cases with two or three features had either benign (n = 27) or metastatic bone disease (n = 10).

CONCLUSION:
Combining bone lesion and lung tumor PET/CT features can help stratify risk of bone metastasis in these patients.

KEY POINTS:
• In NSCLC with a single-bone FDG lesion, lesion SUVmaxis useful for differential diagnosis. • CT features of the single-bone FDG lesions provide additional diagnostic value. • High NSCLC SUVmax, greater T stage, and FDG positive nodes also favor metastasis.

Author information

Lim CH1, Ahn TR2, Moon SH1, Cho YS1, Choi JY1, Kim BT1, Lee KH3.
1
Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul, 06351, South Korea.
2
Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, 06351, South Korea.
3
Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul, 06351, South Korea. khnm.lee@samsung.com.