Table 2. Responses to Survey Questions 2-13 and 17-18.
Descriptive statistics on the surveyed center’s SRS volume, type, and machine are included as ranges and means. Additionally, responses regarding SRS and SL-SRS practices are included as percentages of total responses.
Abbreviations: US – United States, SRS – stereotactic radiosurgery, GK – Gamma knife, LINAC – linear accelerator, CNS – central nervous system.
| Questions | Responses |
| Total number of cases treated with radiosurgery at your institute last year (2021). | Mean: 406 cases Range: 168-741 cases |
| Number of brain metastases patients treated with radiosurgery per year. | US Range: 25-85.7% International Range: 2-53% |
| Does your institution have a formal or informal upper limit on a number of brain metastases treatable with SRS (in 1-5 fractions)? If yes, what is that limit? | 60% No limit 40% Upper limit exists, range 15-25 mets |
| What percentage of your SRS-treated brain metastases patients had this number of lesions treated at the time of SRS? | Average 1-4 lesions: 68.1%, 5-10 lesions: 20.2%, 11-15 lesions: 6.5%, 16-20 lesions: 3.5%, 21+ lesions: 1.6% |
| Which machine(s) does your institute use for SRS? | GK: 100% of institutions LINAC: 20% of institutions |
| Percentage of cases treated with frame or mask-based immobilization or combination. | Frame-based cases: 71% Mask-based cases: 28% Combination cases: <1% |
| Percentage of cases treated with single fraction SRS, hypofractionated SRS, and combined single fraction/hypofractionation in one patient | Single Fraction cases: 83% Hypofractionated cases: 16% Combined cases: <1% |
| Does your institution use selective lesion SRS? | 80% Yes 20% No |
| Are there any established clinical indications for selected lesion SRS at your institution? | 20% Yes 80% No |
| Are there research protocols in your institution that would take priority over a selected lesion approach for patients with multiple brain metastases? | 10% Yes 90% No |
| Are there clinical trials at your institution that specifically request selected lesion SRS in order to study the effect of a drug in CNS? | 10% Yes 90% No |
| What is your cutoff size (largest dimension, or volume) for SRS for lesions in eloquent areas such as the brainstem or motor cortex? | a) 5mm/0.065cc 0% b) 10mm/0.52cc 0% c) 20mm/4.19cc 20% d) 25mm/8.18cc 10% e) 30mm/14.14cc 60% f) No cutoff 10% |
| What is your cutoff size for SRS for lesions in non-eloquent areas (largest dimension, or if volumetric cut off, diameter of equivalent circle)? | a) 10mm/0.52cc 0% b) 20mm/4.19cc 0% c) 25mm/8.18cc 0% d) 30mm/14.14cc 30% e) 40mm/33.51cc 60% f) No cutoff 10% |