Treatment of patients with brain metastases is heterogeneous. WBRT is a standard therapy, with the addition of surgery or SRS to WBRT, or SRS used alone, reserved for selected patients on the basis of their clinical characteristics. One potential advantage of local therapy may be avoiding the toxicity of WBRT [12–14]. However, SRS, when used alone, has several disadvantages. SRS alone has been shown to be inferior to the combination of SRS with WBRT for durable local control and distant intracranial control . When studying patients initially undergoing any local therapy – surgery or SRS – more patients required salvage if treated without WBRT . Long-term cognitive outcomes have been shown to be more closely correlated with intracranial progression than with treatment modality, emphasizing the significance of intracranial control over short-term side effects [21, 22].
Given the limited scope of current studies and the variability in outcomes, National Comprehensive Cancer Network (NCCN) guidelines allow for a wide range of treatment options including WBRT, surgical resection, or SRS, alone or in combinations . Previous reviews of treatment patterns have demonstrated stable rates of surgery since the 1980s, with an increasing use of SRS . Despite clinical trials limiting eligible patients to those with limited central nervous system disease, a recent survey demonstrated that more than half of physician respondents would consider using SRS as an initial treatment for patients with 5 or more intracranial lesions . The increased utilization of SRS as well as the persistent heterogeneity in practice may be due to the time of dissemination of research into clinical practice, or the time to purchase and adoption of new technologies.
With mixed evidence and a heterogeneous patient population, treatment decision-making is complex. Significantly, our study demonstrates that although clinical factors, such as number of lesions and patient age, affected treatment selection, physician practice environment had a strong, independent effect on the use of SRS.
Factors related to the patient’s clinical condition affected treatment selection. There was increased use of WBRT for increasing number of lesions, which is consistent with the lack of evidence to support the use of local techniques for patients with numerous metastases. However, we observed that a substantial proportion of physicians still chose SRS as part of their approach for patients with multiple lesions, particularly for patients with 3 lesions. The increased use of SRS with 3 lesions as compared with 1 was possibly due to the use of surgery for a substantial proportion of patients with 1 lesion, and due to the use of SRS combined with WBRT in patients with 3 lesions. Interestingly, physicians overall selected WBRT for patients with 1, 3, or 8 lesions more often for patients who were frail (increased age, low KPS) and might suffer increased morbidity from WBRT. This finding was unexpected, since WBRT has been shown to cause side effects that might be difficult for frail patients with limited life expectancy to tolerate, such as increasing fatigue, worsening physical function, and deterioration of appetite [7, 14, 26]. Additional clinical factors may influence treatment selection, but were not addressed in this study, including tumor location and surgical accessibility; additional treatment options not evaluated include the use of SRS in combination with surgery, chemotherapy, and the role of hospice.
Practice environment and clinical expertise also influenced the use of SRS, even when controlling for clinical factors. Although practice type was not associated with the preference for SRS, the availability of SRS was significantly associated with its use, indicating that patients are more likely to receive this treatment if the physician they see practices it herself or has it available within her practice. This pattern of care could lead to under- or over-utilization of SRS: patients may have treatment guided more by a provider’s practice than by the patient’s clinical condition. Previous studies have demonstrated the association of physician specialization, board certification, treatment volume and time in practice with other cancer-related treatment decisions [27, 28]. For example, diagnostic imaging use has increased when such imaging is performed at a self-referred facility . Similarly, radiation oncologists may be prescribing complex treatment approaches more frequently when they have access to the facilities or equipment. Alternatively, this propensity for increased use of SRS with easy access may relate to physicians’ familiarity with their own clinical outcomes when using new technology. Our respondents may also have rates of access to SRS that are not comparable to those available nationwide, since the ACR survey did not report on the availability of SRS equipment.
Our study has several limitations due to its reliance on physician self-report as a proxy for practice, its timing, and the limited number of respondents. Clinical scenarios were hypothetical and treatment options were limited. Although physician surveys have shown a strong correlation between vignettes and actual practice , further objective validation of these data would be desirable, as the vignettes used in this survey were novel. Respondents to this survey were dominantly radiation oncologists, whose treatment decisions may be greatly impacted by other members of the inter-disciplinary oncology team not represented in this survey. Rates of radiosurgery utilization more than doubled between 2000 and 2005, so continued increases in the use of radiosurgery could have occurred since the completion of this survey . Additional research has been published since 2008 that may have resulted in further shifts in practice patterns.
The limited number of respondents to our survey limits the generalizability of our findings. The response rate of 6% may indicate that the practice patterns outlined in this study are specific to a subgroup of clinicians with particular interest or expertise in radiosurgery and may not be indicative of global patterns of care. Although respondents were similar to those in the ACR survey, the comparison is limited due to the nature of the variables available; key issues, such as expertise with SRS or volume of patients brain metastases, were not available in the ACR survey for comparison. However, ours is the first study to document practice patterns using vignettes in this clinical setting.