Is 18F-FDG PET/CT more reliable than 99mTc-MDP planar bone scintigraphy in detecting bone metastasis in nasopharyngeal carcinoma?

Objectives Bone metastasis occurs frequently in nasopharyngeal carcinoma (NPC) patients. The aim of this study was to compare the clinical value of 18F-FDG PET/CT with that of 99mTc-MDP planar bone scintigraphy (PBS) for detecting bone metastasis in NPC patients.

Methods Thirty-five histologically proven NPC patients were enrolled in this retrospective study. They underwent both 18F-FDG PET/CT and PBS within 7 days in our department. In a lesion-based analysis, the skeletal system, excluding the head, was divided into four regions: the spine (including the whole vertebral column), the pelvis (including the iliac, ischial, and pubic bones), the thorax (including ribs and sternum), and the appendix (including extremities, scapulae, and clavicles). Bone metastasis was considered to be present if there was any reliable evidence identified within 6 months follow-up. PET/CT and PBS were compared using McNemar’s paired-sample test.

Results Fifteen (42.9%) of 35 eligible patients were found to have bone metastasis. In a patient-based analysis, the sensitivity, specificity and accuracy of PET/CT was 60.0% (9/15), 100% (20/20) and 82.9% (29/35); as for PBS, it was 66.7% (10/15), 85.0% (17/20) and 77.1% (27/35), respectively. There was no statistical difference between PET/CT and PBS (P>0.05). In a lesion-based analysis, a total of 50 lesions were confirmed to be malignant (spine: 27, thorax: 11, pelvis: 8 and appendix: 4). Although PET/CT was found to be more sensitive than PBS (sensitivity: 70.0% vs 42.0%; P=0.044), there were still 14 metastatic (28.0%) lesions could be detected by PBS while negative in PET/CT imaging. Besides, both PET/CT and PBS missed 1 spine lesion.

Conclusions PBS, as a conventional imaging, should be used as a complement for detecting bone metastasis in NPC patients.