Comparison of FDG PET/CT to bone scan for detection of bone metastases in breast cancer

Objectives Bone is the most frequent site of breast cancer metastases.Considering many breast cancer patients are old age,bone is likely affected by degenerative or inflammatory bone disease.Recently PET/CT has become an alternative study which could provide an accurate and efficient tool for detection of primary and metastatic foci.The purpose of this study was to compare the accuracy between PET/CT and bone scan for detecting bone metastases in breast cancer.

Methods One hundred and seventy-eight patients with breast cancer underwent PET/CT together with bone scan within 1 month between July and November 2011 for restaging and initial staging were included.Bone metastases was assessed by clinical and radiological follow up for at least 6 months.

Results Nine patients had bone metastases confirmed during follow-up.PET/CT was considered positive for bone metastasis in 11 pts.The sensitivity,specificity,positive predictive value and negative predictive values of PET/CT were 77%,97%,63% and 98% respectively.Bone scan was interpreted as positive in 10 pts.The sensitivity,specificity,positive predictive value and negative predictive values of bone scan were 88%,98%,80% and 99% respectively.The sensitivity,specificity and accuracy of bone scan were slightly higher than those of PET/CT but there was no statistically significant difference between PET/CT and bone scan(P=0.4). Two pts with false-negative finding on PET/CT had positive finding with bone scan.One of these pts had a osteoblastic metastasis in the sternum body that was missed on PET/CT and chest CT.On the other hand,there is one pt with bone metastasis that have been exclusively detected by PET/CT.

Conclusions The difference between bone scan and PET/CT for detection of bone metastases may be attributable to the different mechanism.Bone scan depends on the osteoblastic response to bone destruction by tumor cells,and FDG-PET/CT detects the metabolic activity of the tumor cells.Therefore FDG PET/CT and bone scan are complementary modalities and bone scan is still important tool to detect bone metastases besides cost.