Oligometastatic brain metastases may be treated with stereotactic radiosurgery (SRS) alone, but no consensus exists as to when SRS alone would be appropriate.  

     A survey was conducted at two radiosurgery meetings to determine which factors SRS practitioners emphasize in recommending SRS alone, and what physician characteristics are associated with recommending SRS alone for >5 metastases.

     95 completed surveys were collected in San Francisco and 54 were collected in Sendai.

     All physicians attending the 8th Congress of the International Stereotactic Radiosurgery Society (ISRS) in June, 2007 in San Francisco, CA and the 18th Annual Meeting of the Japanese Society of Stereotactic Radiosurgery in Sendai, Japan in July, 2009 were asked to complete a questionnaire ranking 14 clinical factors on a 5-point Likert-type scale (1=none; 5=very strong) to determine how much each factor might influence a decision to recommend SRS alone for brain metastases. Results were condensed into a single dichotomous outcome variable of “influential” (4-5) vs. all others (1-3). Respondents were also asked to complete the statement: “In general, a reasonable number of brain metastases treatable by SRS alone would be, at most, ......” The characteristics of physicians willing to recommend SRS alone for >5 metastases were assessed (univariate: ?2; multivariate (MVA): logistic regression).

     Both surveys included experienced academicians and private practitioners; over 70% had performed SRS for more than 5 years. A substantial majority (65.3% and 83.3%) treated >30 cases brain metastases/year with SRS.  In the survey conducted in San Francisco, the most influential characteristics were KPS (78%), presence/absence of mass effect (76%) and systemic disease control (63%).  In Sendai, the most influential characteristics were the size of the metastases (78%), the KPS (70%), and metastasis location (68%).  In San Francisco, 55% of respondents considered treating >5 metastases “reasonable”, including 77.1% of private practitioners vs. 44.4% of academicians (?2, p=0.002), 68.6% of neurosurgeons vs. 38.6% of radiation oncologists (p=0.003), and 72% of Gamma Knife users vs. 34.9% of linear accelerator users (p=0.002). In Sendai, 83% of respondents considered treating >5 metastases “reasonable”, including 88.5% of private practitioners vs. 68.8% of academicians (?2, p=0.017), 92.7% of neurosurgeons vs. 53.8% of radiation oncologists (p=0.001), and 100% of Gamma Knife users vs. 67.9% of linear accelerator users (p=0.002). A multivariate analysis (MVA) of the San Francisco survey data showed that neurosurgeons (p=0.033) and Gamma Knife users (p=0.002) were significantly more likely to treat >5 metastases with SRS alone, and this finding appeared to be substantiated and extended by the data obtained in Sendai.

     This is a retrospective study.

     No clear consensus exists for how many metastases are reasonable to treat with SRS alone or what factors should be used to assess candidate patients.

     Data collected to assess attitudes and beliefs of experienced physicians indicates that there is a broad, but not universal willingness (that may be increasing over time) to extend the use of radiosurgery for >5 brain metastases.