Radiotherapy for neuropathic pain due to bone metastases
Neuropathic bone pain (NBP) due to bone metastases is estimated to affect about 15-25% of cancer patients experiencing pain. Numerous randomized trials have shown that single or multiple fraction radiotherapy (RT) for painful bone metastases produces intention-to-treat overall response rates (RRs) of approximately 60%, but there are few data on RT for NBP, per se. One randomized trial, Trans Tasman Radiation Oncology Group (TROG) 96.05 showed similar outcomes for NBP, although a single 8 Gy fraction was not proven to be as effective as fractionated treatment (20 Gy in five fractions), with RRs of 53% and 61%, respectively. A recent small, single institution series reported a comparable overall RR for NBP using a variety of fractionation schedules. Although TROG 96.05 found no statistically significant difference in the rates of re-treatment, spinal cord compression, or pathological fracture at the index site by arm, one subsequent single institution retrospective review cautioned against using single fractions for spine (the skeletal site causing the vast majority of NBP), particularly in the presence of high “spinal instability” scores. In that study, single fractions were associated with more spinal adverse events (including symptomatic vertebral compression fracture and spinal cord compression) than fractionated schedules. Although re-irradiation of bone metastases is feasible and moderately effective, there are no outcome data specific to re-treatment of NBP. In summary, NBP may appropriately be treated with fractionated RT, although single fractions may also be reasonable for patients with poor performance status and/or limited expected survival, and in centers with prolonged waiting times for fractionated treatment, given that re-treatment is possible for either. In addition, multiple fractions may be preferable for vertebral metastases in the setting of high “spinal instability” risk.
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