Brain Metastases

Up to 50% of all patients with malignancies will develop brain metastases and, after radiotherapy alone, more than half of these will die from progressive neurological disease.

In the past, surgical excision of metastatic tumours, if possible, combined with whole brain radiotherapy was thought to be the treatment of choice for metastases.

However metastases may reoccur locally after excision. Some types of metastasis are resistant to radiotherapy. If new metastases appear after radiotherapy, further similar treatment cannot usually be given.

Gamma Knife has several advantages. Its success rate is better than surgery because there is less chance of local recurrence. It is effective on all types of metastasis. Repeat treatment is possible if new metastases occur. Also it takes only one day – surgery and radiotherapy combined last at least one month.

International recommendations are to perform only Gamma Knife treatment and to repeat this if new lesions occur. The only exception is when a large metastasis is causing pressure effects and needs decompressive craniotomy and removal urgently, or when there are so many lesions that radiosurgery is impractical. Gamma Knife can control most brain metastases so that the prognosis then depends on whether there is other disease outside the brain.

Several studies have shown that Gamma Knife treatment of single metastases can produce tumour control and survival as good as surgery plus WBRT (1). Moreover the results for Gamma Knife are the same for multiple metastases as for a single lesion (2), the chance of local recurrence is less than after surgical removal and control does not depend on the histological diagnosis. Since radiosurgery is more cost effective, easier for the patient and has a much lower complication rate, it would seem that the only indications for surgery are rapid neurological deterioration due to mass effect and the large (>3.5cm) diameter single lesion especially in the posterior fossa where any temporary oedema due to radiation would have serious results. The remaining indications for WBRT are multiple tumours (>10-15) or miliary lesions and CSF seeding.

Gamma Knife treatment can control >90% of metastatic brain tumours and complications, usually transient swelling after about 9 months which is controllable by steroids, occur in 5-10% (3). 80% 3 year survival has been achieved in cases where the extracranial disease has been controlled (4).

In a comparison of Gamma Knife treatment with WBRT the quantity and quality of survival was better with Gamma Knife (5). It is not clear how much benefit WBRT has in preventing new metastases since these may develop by new spread after treatment has finished. Accordingly the present recommendation is to repeat Gamma Knife surgery as necessary and avoid all WBRT. In this way patients will not die from the brain metastases and prognosis depends only on the extracranial disease.

REFERENCES

1. Muacevic A, Kreth FW, Horstmann GA et al. Surgery and radiotherapy compared with gamma knife radiosurgery in the treatment of solitary cerebral metastases of small diameter. J Neurosurg 1999; 91: 35-43.
2. Kondziolka D, Patel A, Lunsford LD et al. Stereotactic radiosurgery plus whole brain radiotherapy versus radiotherapy alone for patients with multiple brain metastases. Int J Radiat Oncol Biol Phys 1999; 45: 427-434.
3. Young RF, Jaques DB, Duma C et al. Gamma knife radiosurgery for treatment of multiple brain metastases. In Alexander E, Kondziolka D, Loeffler J (eds) Radiosurgery, Basel, Karger, 1996; pp 92-101.
4. Yamanaka K, Iwai Y, Nakajima H et al. Gamma knife radiosurgery for metastatic brain tumour: the usefulness of repeated gamma knife radiosurgery for recurrent cases. Stereotact Funct Neurosurg 1999; 72 (suppl 1): 73-80.