To assess the addition value of ¹⁸F-Fluorodeoxyglucose (FDG) PET/computed tomography (FDG-PET/CT) vs. CT in detecting early metastatic deposits in bone marrow (BM).

From January 2009 to December 2010, 198 consecutive patients (88 male, 110 female; median age: 64 years) were retrospectively examined. All patients underwent ¹⁸F-FDG-PET/CT for disease evaluation: 65 for lung cancer, 66 for breast cancer, 57 for lymphoma and 10 for multiple myeloma. All scans were reviewed by a radiologist and a specialist in nuclear medicine for the identification of bone lesions. The presence of BM metastases was confirmed by biopsy, sequential PET/CT scan or magnetic resonance imaging when available. A patient-based analysis was performed.

Investigating the presence of skeletal metastasis, 94 (48%) patients had positive and 104 (52%) negative CT scan whereas 110 (56%) had positive and 88 (44%) negative FDG-PET/CT scan (P<0.001). The two imaging modalities were concordant in 178 (90%) patients for bone lesions; on the contrary 20 (10%) patients had discordant results (P<0.001). In 21 out of 178 concordant patients BM lesions were identified both in CT and FDG-PET, whereas nine out of the 20 discordant patients showed BM involvement at PET/CT only. Overall, PET/CT was able to identify 30 (15%) patients with BM lesions. In these latter patients, the maximum standardized uptake value (SUVmax) for BM metastases was 7.9±4.5 (range: 3.1–19.0), resulting slightly higher in patients with negative than positive CT scan (8.3±5.1 vs. 7.8±4.3, respectively; P=0.79).

FDG-PET/CT resulted more accurate than CT in early detection of BM metastases. The FDG-PET/CT images improve the staging of about 15% of our study population. PET/CT detected BM lesions mainly on the basis of their increased metabolic activity rather than on anatomical alterations. Moreover, it provided an accurate identification of tumour viability that was useful for treatment planning and follow-up.