Evaluating remineralization in breast cancer patients with osteolytic bone metastases undergoing palliative radiotherapy using computerized tomography (CT) density measurements — a feasibility study

Abstract

Purpose/Objective: Bone metastasis is common in patients with advanced breast cancer. Radiotherapy has been very effective in palliating the symptoms but there is no dose response relationship in terms of pain relief. Fractures can occur in these patients, especially those with a prolonged survival. High dose radiotherapy can inhibit osteoblastic activity and interfere with bone healing. There was an increased fracture rate in the previous Radiation Therapy Oncology Group (RTOG) study with higher doses. On the contrary, in recent trials, there were more fracture events in patients receiving lower doses of radiation. What the optimal dose in preventing fracture remains unknown. There is a clear relationship between reduced bone density and increased fracture risk. It is logical to evaluate whether there is a dose response relationship with remineralization. The aims of the study were to examine the feasibility of evaluating the degree of remineralization resulting from palliative radiotherapy with CT density measurements and to correlate such with the pain relief. Materials/Methods: Breast cancer patients with osteolytic metastases who received palliative radiotherapy were invited for the study. Patients with recent change (within four weeks of delivery of radiotherapy) of chemotherapy, hormonal therapy and bisphosphonates were excluded. CT scans were performed at the irradiated site before and 3 months after the delivery of palliative radiotherapy. The pain data at the irradiated site were collected. Two musculoskeletal radiologists contoured the lytic irradiated areas with the CT density measured and % density change was reported. Results: Twenty-five patients completed the study. The dose fractionation regimes were: single 8 Gy (3 patients), 20 Gy in 5 daily fractions (17 patients) and 30 Gy in 10 patients (5 patients). The median % density change of the single 8 Gy, 20 Gy/5#, 30 Gy/10# were: 128 (range 98–225), 141 (range 105–166), and 145 (range 65–235), respectively. There was direct correlation between pain relief and improved remineralization. Conclusions: Our study confirms it is feasible to evaluate remineralization of osteolytic lesions with palliative radiotherapy. Larger studies are required to test whether there is a dose-response relationship with regard to remineralization and its relationship to subsequent fractures.