Validation of American College of Radiology Bone Reporting and Data System (Bone-RADS) Version 2023 for diagnosis of malignant tumors of appendicular bone on conventional radiographs

Purpose: To evaluate the diagnostic performance of the American College of Radiology(ACR) Bone Reporting and Data System (Bone-RADS) in diagnosis of malignant tumors of the appendicular bone on conventional radiographs.

Methods: Primary and secondary tumors of appendicular bone in patients who underwent radiographic and MRI examinations were classified into benign, intermediate, and malignant using a reference standard of histopathology, imaging follow-up, or clinical-radiologic consensus. Two radiologists assessed five radiographic features (margin, periosteal reaction, endosteal erosion, pathologic fracture, and extra-osseous mass), scored point total (points from radiographic features and a history of cancer), and assigned Bone-RADS categories. The diagnostic performance of Bone-RADS and interreader agreements were calculated.

Results: A total of 778 patients (507 benign, 45 intermediate, and 226 malignant tumors) were included. Bone-RADS showed high discrimination performance, with areas under the receiver-operating characteristics curve of 0.940-0.957 for point total and 0.895-0.900 for categorization. Bone-RADS had high sensitivity (95.2 %-99.1 %) and negative predictive value (NPV) (96.4 %-99.5 %), but relatively low specificity (65.0 %-68.6 %) and positive predictive value (PPV) (53.7 %-61.9 %). Interreader agreements were good to excellent for Bone-RADS point total (ICC = 0.850), categorization (k = 0.739), and most of the radiographic features (k = 0.621-0.822), except for endosteal erosion (k = 0.537) and extra-osseous mass (k = 0.234).

Conclusion: In diagnosis of malignant bone tumors, ACR Bone-RADS showed high discrimination performance, with high sensitivity and NPV, but relatively low specificity and PPV. Nevertheless, relatively low interobserver agreement in some radiographic features and the consensus-based points system in Bone-RADS warrant further research and possible updates.