The re treatment of metastatic bone disease
The re-treatment of metastatic bone disease causing recurrent pain after an initial course of EBRT was seen to be feasible with a reasonable rate of symptom relief [13–19]. In echoing the ACR findings, the task force noted that the available data was derived from studies where re-treatment was not the primary endpoint studied, and that many of the descriptions of re-treatment were based upon small numbers of patients. Additionally, the authors cautioned that re-treatment may only be considered when taking into account the normal tissue tolerance of structures included in the treated volumes. The spinal cord and cauda equina were specifically mentioned as structures whose tolerance to the combined dosing must be taken into account when delivering a second course of EBRT to the spine.
Given significant interest in newer technologies amongst radiation oncologists and neurosurgeons, the ASTRO task force enthusiastically recognized the promise for improvements in care with highly conformal therapy which includes all technologies that can deliver higher doses to metastatic bone disease with a steep dose gradient to spare adjacent normal structures. The team focused their analysis on the potential benefits of stereotactic body radiation therapy (SBRT) for metastases in spine bones, though they described that the available data for this intervention has to this point been accrued in single institutional studies with small numbers of patients whose responses have been measured with novel treatment outcomes. As such, the task force suggested that patients who receive SBRT should strongly be considered for the available treatment protocols to better accrue data about efficacy and toxicity measures. The theoretical advantage of SBRT for sparing spinal cord or cauda equina in the re-treatment of recurrent, painful spine lesions was documented in much greater detail than was true in the ACR Appropriateness Criteria [27–32].
In an attempt to clarify confusion regarding the use of radiotherapy with other available interventions for painful metastatic bone disease, the ASTRO task force clearly stated that EBRT is still necessary in situations where patients receive surgery for spinal cord pkc inhibitors or long bone stabilization, intravenous radiopharmaceuticals for widespread bone disease, osteoclast inhibitors, or kyphoplasty or vertebroplasty for lytic lesions causing spinal instability [33–36]. Surgery was only recommended for patients with spinal cord compression who have a favorable prognosis and sufficient performance status to warrant the surgical risks and post-operative rehabilitation required for that degree of intervention. Radiopharmaceuticals were deemed most appropriate in patients with widespread, painful osteoblastic metastases that are apparent on a technetium-99 bone scan. While the use of osteoclast inhibitors was seen as being a reasonable means by which to palliate bone pain and promote re-ossification, the task force pointed out that there are no data to suggest that the palliation of a single site of metastatic bone pain is superior with osteoclast inhibitors plus EBRT versus EBRT alone. Finally, the task force described the theoretical advantage of using kyphoplasty or vertebroplasty for spinal instability caused by lytic metastases, though they shared the belief that the data proving those assumptions was mostly derived from retrospective, single institutional studies. In its conclusions, the ASTRO group suggested that future bone metastases treatment trials should be made uniform by the measurement of consistent variables as defined by the International Consensus on Palliative Radiotherapy Endpoints while also assessing functional domains and quality of life with validated instruments such as the European Organization for Research and Treatment of Cancer bone metastases quality-of-life questionnaire [24,37].
National Comprehensive Cancer Network (NCCN) and bone metastases treatment recommendations The National Comprehensive Cancer Network is made up of experts from cancer centers of excellence around the United States who designate representatives to committees that evaluate data and provide treatment options for most common cancers . While there is no specific NCCN group designated to evaluate the use of radiotherapy for bone metastases, the topic is dealt with to varying degrees in the publications which deal with primary diagnoses that are most likely to metastasize to bone. The NCCN Guidelines also include a wider variety of author specialty types for each clinical site than do the ACR and ASTRO guidelines. Furthermore, while radiation oncologists make up the majority of panel members on the ACR and ASTRO committees, radiation oncologists generally make up a distinct minority, or are a singular member, of the NCCN committees. As such, the NCCN guideline recommendations regarding radiotherapy for bone metastases are likely to result from less vigorous conversations and voting criteria than might be true for those offered by the ACR and ASTRO groups.