181stantial survival benefits [ 33 ]. Alternatively, hav-
ing more than three or four small metastases in
eloquent brain or in a patient with rampant extra-
cranial disease would be a relative contraindica-
tion for surgical intervention, and WBRT or SRS
coupled with chemotherapy may be considered.
In cases of asymptomatic patients with lesions in
the posterior fossa, SRS is an excellent treatment
choice (Figs. 13.3 and 13.4). This approach is
even more attractive if multiple metastatic lesions
are present in both the supratentorial and the
infratentorial compartments in asymptomatic
patients (Fig. 13.5). Even tumors thought to be
moderately or highly “radioresistant” (i.e., mela-
noma, renal cell carcinoma, thyroid, non-small-
cell lung cancer, colon) may benefit from SRS
when WBRT might otherwise not prove to be
efficacious. There is good evidence to suggest
that the mechanism of SRS-induced cell death
may be different than that of WBRT [ 34 ]. This is
discussed later in this chapter. Nevertheless, SRS
has been shown to be equivalent to surgical
intervention in up to four metastatic lesions, but
some surgeons contend that safe, effective radio-
surgery can be performed for patients with up to
ten metastases [ 35 ].
Tumors of the posterior fossa represent a
unique challenge for the neurosurgeon. Normally
a contraindication to surgical intervention, mul-
tiple metastases or single, relatively inaccessibleFig. 13.2 (a, b) Axial CT images of right occipital con-
dyle lesion initially thought to be a paraganglioma but
confirmed a metastatic lung adenocarcinoma by needle
biopsy. (c, d) T1-weighted axial MRI with and without
gadolinium enhancement. (e) Positron emission tomogra-
phy image consistent with active tumor. (f, g) Coronal
T1-weighted MRI with and without gadolinium enhance-
ment. (h) FLAIR imaging. (i) T2-weighted axial MRI. (j)
Radiosurgical isodose treatment planning lines for this
lesion treated with stereotactic radiosurgery13 Metastasis to the Posterior Fossa