Is the assessment of the central skeleton sufficient for osseous staging in breast cancer patients? A retrospective approach using bone scans.

OBJECTIVE: By analyzing bone scans we aimed to determine whether the assessment of the central skeleton is sufficient for osseous staging in breast cancer patients. This might be of interest for future staging modalities, especially positron emission tomography/computed tomography, usually sparing the peripheral extremities, as well as the skull.
MATERIALS AND METHODS: In this retrospective study, a total of 837 bone scans for initial staging or restaging of breast cancer were included. A total of 291 bone scans in 172 patients were positive for bone metastases. The localization and distribution of the metastases were re-evaluated by two readers in consensus. The extent of the central skeleton involvement was correlated to the incidence of peripheral metastases.
RESULTS: In all 172 patients bone metastases were seen in the central skeleton (including the proximal third of humerus and femur). In 34 patients (19.8 %) peripheral metastases of the extremities (distally of the proximal third of humerus and femur) could be detected. Sixty-four patients (37.2 %) showed metastases of the skull. Summarizing the metastases of the distal extremities and skull, 79 patients (45.9 %) had peripheral metastases. None of the patients showed peripheral metastases without any affliction of the central skeleton. The incidence of peripheral metastases significantly correlated with the extent of central skeleton involvement (p<0.001).
CONCLUSIONS: Regarding bone scans, an isolated metastatic spread to the peripheral skeleton without any manifestation in the central skeleton seems to be the exception. Thus, the assessment of the central skeleton should be sufficient in osseous breast cancer staging and restaging. However, in case of central metastases, additional imaging of the periphery should be considered for staging and restaging.