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Considerations in the Diagnosis and Management of Brain Metastases

Considerations in the Diagnosis and Management of Brain Metastases

Dr. Sawaya’s review provides a comprehensive overview and
excellent summary of current knowledge on an important topic. Brain metastases
far outnumber primary brain tumors; their diagnosis and treatment are
bread-and-butter for both medical and neurosurgical oncologists. Additionally,
unlike primary brain tumors, a definable at-risk population exists for brain
metastases, making prevention a potentially achievable goal.

Diagnosis

As Dr. Sawaya points out, however, many brain metastases are asymptomatic.
Diagnosis and treatment before symptoms develop are important. When brain
imaging is included in a "staging" work-up, magnetic resonance imaging
(MRI) with and without gadolinium should be used rather than computed tomography
(CT) because of its greater sensitivity. Most asymptomatic metastases are less
than 1 cm in diameter, and many are only a few millimeters in size. Although MRI
with "triple-dose" gadolinium is considered by some to be even more
sensitive than standard contrast imaging, we have used standard contrast MRI
with careful attention to the imaging sequences that highlight edema around
small metastases. The fluid-attenuated inversion recovery (FLAIR) sequence is
probably best for this purpose.

When a metastasis has a ring-enhancing appearance with surrounding edema,
brain abscess is an important differential consideration. The characteristic
bright appearance of abscesses on diffusion-weighted imaging is helpful in this
regard, because the necrotic centers of most ring-enhancing metastases will show
low or intermediate signal intensity.

We find that most brain metastases can be confidently diagnosed without
obtaining tissue. In some situations, such as a single brain lesion with no
known systemic cancer or with a chest primary of unknown histology that cannot
be biopsied without thoracotomy, biopsy of a brain metastasis is necessary for
diagnosis. Interstitial brachytherapy can be performed at the same sitting in
this situation, using a probe introduced stereotactically into the center of the
tumor to deliver in a few minutes a therapeutic single-fraction treatment
equivalent to radiosurgery.[1]

Medical Treatment

As Dr. Sawaya notes, corticosteroids are indicated for most patients with
brain metastases, especially those with neurologic symptoms. An exception occurs
when brain lymphoma is a diagnostic consideration, because even a brief course
of steroid treatment can cause complete regression of these lesions, thus
thwarting biopsy.

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