Contemporary Approaches to Cancer Bone Pain
Ultrasound Thermal Therapy Cuts Pain from Bone Metastases
Bone pain is one of the most common complications of cancer, occurring in one-third or more of patients with bone metastases, especially in those with lung, breast, or prostate cancer.1 If not controlled, cancer-induced bone pain (CIBP) may increase disability, cause depression and anxiety, and negatively affect patients' quality of life.1,2 Following the WHO analgesic ladder—starting with non-opioid analgesics and stepping up first to weak opioids with non-opioid adjuncts and then to strong opioids—cancer pain is controlled in most patients, but as many as 20% require more aggressive therapy.3
Cancer-induced bone pain typically consists of background pain punctuated by breakthrough pain and results from complex mechanisms that vary in different tumor types.1,4 Because the neurobiology of CIBP differs from that of either inflammatory or neuropathic pain and may rely on different pathways in different individuals, a wide range of responses to analgesic treatment is common.4 Most patients require a combination of approaches to adequately treat their pain.4 Fortunately, many options are available for treatment of CIBP, and recent research has provided new insights into how this debilitating complication may be optimally managed.
New Approaches in Radiotherapy
Radiotherapy is regarded as the gold standard for treatment of CIBP, even though it provides complete pain relief in only one-fourth of patients and 50% relief in half.1,2 In addition, as many as 40% of patients experience pain flares, a transient worsening of pain.5 Patients with spinal metastases present a particular challenge because the spinal cord is particularly sensitive to radiation, but a new approach may offer a safer alternative.6 Stereotactic body radiotherapy (SBRT) uses image guidance to precisely deliver high-dose radiation to tumors while protecting the spinal cord.6
The clinical benefit of SBRT was investigated in a phase I-II study of 149 patients with spinal metastases from a variety of cancers.6 All patients underwent CT-guided SBRT, receiving a total radiation dose of 27-30Gy, typically in three fractions. The 10Gy volume received by the spinal cord was limited to 0.01 cm3. The proportion of patients reporting no pain rose from 26% at baseline to 39% at 4 weeks and continued to climb during follow-up, reaching 54% at 6 months (P <0.0001 vs. baseline) among the 102 patients still in the study. Toxic effects were mild, and no radiation-related spinal cord myelopathy was observed, suggesting that SBRT may find an important role in this vulnerable population.