Palliative radiotherapy for bone metastases: conventional external beam radiotherapy.

Conventional external beam radiotherapy (cEBRT) is effective for managing symptomatic bone metastases and continues to be in demand despite advances in stereotactic body radiotherapy. This review provides an overview of cEBRT for bone metastases, with a focus on the following: (1) Initial palliative radiotherapy: randomized controlled trials and meta-analyses have shown that single-fraction cEBRT at 8 Gy is as effective as multifractionated cEBRT for reducing pain due to bone metastases. Single-fraction cEBRT at 8 Gy may be a reasonable option for bone metastases with neuropathic pain in consideration of the burden on patients. The efficacy of radiotherapy for preventing skeletal-related events in bone metastases remains unclear. Prophylactic fixation followed by radiotherapy is recommended for long-bone metastases at high risk of fracture. (2) Palliative reirradiation: reirradiation is indicated for patients with insufficient pain relief or pain progression after initial radiotherapy for bone metastases. In palliative reirradiation for spinal metastases, the tolerance dose of the spinal cord needs to be carefully considered due to the risk of radiation myelitis. (3) Treatment strategies for metastatic spinal cord compression (MSCC) or spinal bone metastases with instability: treatment decisions for MSCC, including radiotherapy or decompression surgery followed by radiotherapy, need to be carefully considered by a multidisciplinary team, including radiation oncologists and orthopedic surgeons. Moderate-dose corticosteroids (dexamethasone bolus of 10-16 mg) are recommended in combination with radiotherapy for MSCC. Spinal instability caused by spinal bone metastases is an indication for fixation surgery, and postoperative radiotherapy needs to be considered.