Monitoring therapeutic response in skeletal metastases using dual-energy X-ray absorptiometry: A prospective feasibility study in breast cancer patients

Response to systemic therapy in breast cancer patients with lytic skeletal metastases manifests as a shift from increased bone resorption to new bone formation. We hypothesized that dual-energy x-ray absorptiometry (DXA) coul d be used to prospectively quantitate changes in bone mineral density (BMD) in metastatic skeletal lesions in breast cancer patients receiving systemi c therapy. Nine metastatic breast cancer patients with one or more assessab le lytic skeletal metastases receiving systemic therapy were prospectively evaluated with DXA, skeletal radiographs, computed tomography (CT), and rad ionuclide bone scans at baseline (t = 0 months, 2 months, and 6 months). Th e median (range) percentage change in BMD in skeletal lesions among patient s responding to systemic therapy was 10.7% (0.1-21.85), 5.0% (-1.3-23.8), a nd 16.7% (-2.0-50.8) at 0-2, 2-6 and 0-6 months, respectively. Changes in B MD between 0-2, and 0-6 months were significant (Wilcoxin signed rank test; p = 0.013 and p = 0.017, respectively). The percentage change in BMD skele tal lesions between 0-2 and 2-6 months correlated with the changes imaged o n skeletal x-rays (Spearman rank order correlation coefficient [R-s] = 0.51 1, p = 0.011) and CTs (R-s = 0.416 p = 0.046) but less so with bone scans ( R-s = 0.293, p = 0.189). It is technically feasible to use DXA To prospecti vely monitor changes in lytic skeletal metastases in breast cancer patients receiving systemic therapy. The BMD of skeletal metastases increases in pa tients responding to treatment and was significantly correlated with the ch anges imaged on skeletal xrays and CTs. Additional studies of DXA to evalua te response in skeletal metastasis are warranted.