INTRODUCTION: Radiosurgery (RS) is gaining increasing acceptance in
the upfront management of brain metastases (BM). It was initially used in
so-called radioresistant metastases (melanoma, renal cell, sarcoma)
because it allowed delivering higher dose to the tumor. Now, RS is also
used for BM of other cancers. The risk of high incidence of new BM questions
the need for associated whole-brain radiotherapy (WBRT). Recent evidence
suggests that RS alone allows avoiding cognitive impairment related
to WBRT, and the latter should be upheld for salvage therapy. Thus the increase
use of RS for single and multiple BM raises new technical challenges
for treatment delivery and dosimetry. We present our single institution experience
focusing on the criteria that led to patients' selection for RS treatment
with Gamma Knife (GK) in lieu of Linac. METHODS: Leksell Gamma Knife
Perfexion (Elekta, Sweden) was installed in July 2010. Currently, the Swiss
federal health care supports the costs of RS for BM with Linac but not
with GK. Therefore, in our center, we always consider first the possibility
to use Linac for this indication, and only select patients for GK in specific situations.
All cases of BM treated with GK were retrospectively reviewed for
criteria yielding to GK indication, clinical information, and treatment
data. Further work in progress includes a posteriori dosimetry comparison
with our Linac planning system (Brainscan V.5.3, Brainlab, Germany).
RESULTS: From July 2010 to March 2012, 20 patients had RS for BM
with GK (7 patients with single BM, and 13 with multiple BM). During
the same period, 31 had Linac-based RS. Primary tumor was melanoma in
9, lung in 7, renal in 2, and gastrointestinal tract in 2 patients. In single
BM, the reason for choosing of GK was the anatomical location close to,
or in highly functional areas (1 motor cortex, 1 thalamic, 1 ventricular, 1
mesio-temporal, 3 deep cerebellar close to the brainstem), especially since
most of these tumors were intended to be treated with high-dose RS (24
Gy at margin) because of their histology (3 melanomas, 1 renal cell). In multiple
BM, the reason for choosing GK in relation with the anatomical location
of the lesions was either technical (limitations of Linac movements,
especially in lower posterior fossa locations) or closeness of multiple
lesions to highly functional areas (typically, multiple posterior fossa BM
close to the brainstem), precluding optimal dosimetry with Linac. Again,
this was made more critical for multiple BM needing high-dose RS (6 melanoma,
2 hypernephroma). CONCLUSION: Radiosurgery for BM may represent
some technical challenge in relation with the anatomical location
and multiplicity of the lesions. These considerations may be accentuated
for so-called radioresistant BM, when higher dose RS in needed. In our experience,
Leksell Gamma Knife Perfexion proves to be useful in addressing
these challenges for the treatment of BM.