This single center study examined outcomes for 62 patients with single brain metastases treated with low dose linac-based stereotactic radiosurgery (LB-SRS) between 2005-2009. Median prescribed dose was 14.5 Gy. Median overall survival was 13.5 months. Significant prognostic factors for overall survival included RPA class, SIR index, use of whole brain radiotherapy, minimum dose over 12 Gy, and tumor volume less than 15cc. Local tumor control and distant intracranial recurrence rates were favorable compared to other studies using higher prescribed doses.

1. Linac-based stereotactic radiosurgery
in single brain metastases treated with
a low prescription dose: a single center
experience.
Sisamón I., Cendales R., Bustos J., Gutierrez J.A., Samblas J., Sallabanda K.
Background Unidad de Radiocirugia. Sanatorio San Francisco de Asis.
Grupo IMO. Madrid.
The minimun radiosurgical dose required to
control brain metastases is still unknown. The aim
of this study is to describe clinical outcomes in patients with
single brain metastases treated with low doses.
Material and Methods
Patients with newly-diagnosed, single-brain metastases treated
with framed-collimator-Linac-based stereotactic radiosurgery
(LB-SRS) between January 2005 and September 2009 were
included. GTV was defined using contrast enhanced CT and MRI
fusion; no margins were added to GTV. OS, local intracranial
relapse free survival (LI-RFS), distant intracranial RFS (DI-RFS),
and prognostic factors were analyzed using the Kaplan-Meyer
method and the Log-Rank test. Multivariate analyses were
performed using the Cox regression model.
Results
62 patients (38 males, 24 females) were eligible. Median age was 58
Cox Regression for Overall survival years (30-85); 58.1% of patients had KPS of 80-90; 74.2% had
metachronic metastasis. Primary tumor was NSCLC 48.4%, breast
HR IC 24.2%, colorectal 6.4%, kidney 3.2% and melanoma 8%. 13% of
WBRT No 1 patients had neurosurgical procedure previous to LB-SRS. WBRT was
used as primary treatment whether before or after LB-SRS in 46.8%.
Yes 0.52 0.273-0.993
SIR index was 1-3 (30%), 4-7 (68.4%), 8-10 (1.6%). Median tumor
SIR 1 1 biggest size was 23 mm (6-40).
Median prescribed dose was 14.5 Gy (10-18) to 90% isodose.
2 2.38 1.123-5.077 47 patients (75.8%) died. Median follow-up was 21.6 months. 12-
3 12.46 1.41-109.97 18/month OS probability was 56.7% and 35.8% respectively. Median
survival time was 13.5 months. Significant prognostic factors
Minimun > 12Gy 1 associated with OS in Kaplan-Meyer analyses were RPA, SIR, WBRT,
minimum dose superior to 12 Gy, and tumor volume <15cc. Multivariate
Dose < 12Gy 1.73 0.9-3.33
analyses reported an HR of 0.52 (CI95% 0.27-0.99) for patients
receiving WBRT, an HR of 2.38 (CI95% 1.12-5.08) for SIR 4-7, and an
HR of 12.5 (1.4-109.9) for SIR 8-10 compared to SIR 1-3 respectively.
27 patients had intracranial relapse: 9 (14.5%) had local relapse(LR),
12 (19.3%) had distant intracranial relapse(DIR), and 6 (9.7%) had
Cox Regression for intracranial recurrence both. Rescue treatment was performed with WBRT(4 patients), new
HR IC course of LB-SRS(10 patients), or neurosurgery(1 patient). The
Neurosurgery No 1 9,12,18-month LI-RFS probability was 94.3%, 84.2%, and 61.7%
Yes 0.346 0.09-1.325 respectively. Median LI-RFS time was 38.4 months. Significant factors
RPA 1 1
associated with LI-RFS were RPA, neurosurgical procedure previous to
LB-SRS, and tumor size <30mm. The only significant factor associated
2 3.033 0.723-12.725
with DI-RFS was the SIR index. Multivariate analyses did not evidence
3 4.178 0.791-22.057
any relevant prognostic factors.
Size (cm) 0a1 1
1a2 4106.2 0-infinit Conclusion
2a3 3296.7 0-infinit Results showed satisfactory data for OS and LI-RFS, and turned out
3 or more 13695.2 0-infinit comparable with those published. The described prescription doses
appear to be effective in single brain metastases.
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