"Several studies already described that [PET/CT] can provide important information in breast cancer staging, especially for the detection of extra axillary lymph nodes and distant metastases, such as bone metastases," said lead study author Dr. Julia Krammer from the Institute of Clinical Radiology and Nuclear Medicine. "As most of the scan protocols spare the skull and peripheral extremities, we determined the distribution of bone metastases on bone scans to find out if restricted scan protocols are sufficient for bone staging."
Krammer and colleagues reviewed 837 bone scans for staging or restaging of breast cancer. Positive findings were correlated to additional imaging techniques and previous and follow-up bone scans for further verification.
In total, 291 bone scans in 172 patients were positive for bone metastases. The localization and distribution pattern of the metastases were then re-evaluated by two readers, who scored the involvement of the central skeleton on a three-point scale and correlated to the incidence of peripheral metastases.
The analysis showed bone metastases in the central skeleton in all 172 patients (100%). In 34 patients (20%), peripheral limb metastases could be detected, and 64 patients (37%) showed metastases of the skull.
Overall, 71 patients (41%) had distal limb and skull peripheral metastases, and no patients exhibited peripheral metastases without the central skeleton being affected, according to the researchers.
"This indicates that PET/CT with a restricted scan protocol would not have lead to wrong bone staging results due to no detected metastases in the periphery," Krammer explained. "Therefore, we regard it as sufficient for initial bone staging. However, if PET/CT exposes bone metastases in the central skeleton, we recommend investigating the periphery for the risk of complications such as pathologic fracture and pain."
Because this is an application of high clinical relevance, Krammer and colleagues will continue their research to determine if certain localizations of bone metastases in the central skeleton can predict the incidence of peripheral metastases.
Another extensive study will focus on clinical benefits and change in therapeutic management if PET/CT is used as a single staging method for breast cancer.