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Palliative radiotherapy in bones
Introduction
Non-spine bone metastases are a common source of pain and morbidity among patients with metastatic cancer. Although their true incidence is unknown, estimates ranging as high as 30% to 70% have been reported during the course of their malignancies among patients with the most common cancer histologies. Radiotherapy is widely recognized as an effective tool in the palliation of bone metastases, providing pain relief in up to 85% of patients with at least 50% reporting a complete pain response at 1 to 2 weeks post-treatment. While national consensus guidelines collectively advise against the use of protracted courses of radiotherapy in the palliation of non-spine bone metastases, questions remain regarding the optimal radiation dose, fractionation, and techniques.
In this chapter, we review the common presentations and indications for the treatment of non-spine bone metastases. We discuss various management approaches as they relate to tumor histology, anatomic location, performance status, and prognosis. Lastly, we provide a broad overview of the current evidence landscape, including the emerging role of complex techniques such as intensity-modulated radiation therapy (IMRT) and stereotactic body radiation therapy (SBRT) in the palliation of non-spine bone metastases.
Indications for palliative radiation
Broadly, the primary indications for palliative radiotherapy in the treatment of non-spine bone metastases are (1) pain refractory to medication management and (2) impending pathologic fracture. Unlike osseous lesions of the spine, progression of non-spine bone metastases is not typically associated with acute neurologic compromise. However, their progression may still lead to significant morbidity among patients with metastatic cancer, resulting in skeletal-related events potentially requiring surgical intervention, symptoms relating to hypercalcemia, debilitating pain, and ultimately functional decline that can impede independent activities of daily living and greatly diminish quality of life.
Approaches to management
Uncomplicated non-spine bone metastases
For patients with symptomatic but “uncomplicated” non-spine bone metastases (i.e., osseous lesions that cause pain but do not pose an immediate threat to mechanical or neurologic function ) current National Comprehensive Cancer Network (NCCN) and American Society for Radiation Oncology (ASTRO) consensus guidelines recommend short-course external beam radiotherapy (EBRT) consisting of 10 fractions or less. Notably, single-fraction treatment with 8 Gy × 1 fraction has emerged as a preferred regimen for many patients, particularly those with poor performance status and/or more limited prognoses. Studies have demonstrated comparable levels of pain control with single-fraction radiotherapy to multifractionated schemes, albeit with higher rates of retreatment among those who received single-fraction treatment, which has been posited as a potential reason for its relatively slow uptake in routine practice. By comparison, for patients with good performance status and longer projected prognoses, higher biologic effective doses may provide more durable local control. This can be achieved by offering multifractionated schemes (e.g., 4 Gy × 5 fractions or 3 Gy × 10 fractions) or SBRT.
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