Stereotactic Radiosurgery in the Management of Brain Metastasis

Michael L. Smith, M.D.; John Y. K. Lee, M.D.

Disclosures

Neurosurg Focus. 2007;22(3) 

In This Article

Is WBRT Needed After SRS?

Whole brain radiation therapy is an accepted treatment modality for brain metastases. As mentioned, the addition of WBRT improves patient survival from 1 to 2 months to 3 to 6 months after the original diagnosis.[6,27] The community standard regimen is 30 Gy delivered in 10 fractions,[12] although other protocols have been investigated. An RTOG study using hyperfractionation demonstrated improved survival and neurological function.[16] How ever, a follow-up randomized trial in which patients received 1.6 Gy twice a day and 54.4 Gy total could not conclusively show improved survival.[33]

Radiation-induced dementia is a serious side effect of WBRT. This complication occurs 6 to 12 months after irradiation and can be very debilitating.[4,14] This raises the question whether WBRT should be used more judiciously. Patients with good KPS scores are likely to live longer and are more likely to benefit from improved cerebral tumor control but are also more likely to suffer delayed dementia after WBRT.

Aoyama and colleagues[3] recently published a randomized controlled trial of 132 patients with up to four metastases each who underwent SRS or SRS followed by WBRT. The primary end point was survival. Secondary end points included functional preservation and radiation toxicity. The Mini Mental Status Examination was used for assessment. This is a rapid but not thorough neuropsychological tool. Consistent with previous retrospective studies,[20,50] Aoyama and colleagues found that SRS alone does not provide as good local or distant control as SRS with WBRT. The elimination of WBRT did not, however, result in shortened survival or an altered level of functional independence. This is similar to the results of a surgical trial published by Patchell et al.[38] in 1998 in which patients were randomly assigned to groups that received resection with or without WBRT. This study also failed to demonstrate a survival advantage with the addition of WBRT. Neither trial was designed as an equivalency study and should not be interpreted as such. Instead, we can conclude that within the power of the predetermined criteria, both studies failed to show a survival advantage with the addition of WBRT if patients are treated with SRS initially or even with resection.

The major reason for withholding WBRT is to avoid the late onset of radiation-induced dementia. Unfortunately, Aoyama et al.[3] used an effective but perhaps insensitive tool to study functional status–the KPS score. The ability to determine radiation-induced dementia and complications may require a more sensitive measure than KPS score. It remains unproven, although intuitive, that an SRS-only treatment plan would reduce the incidence of radiation-induced dementia.

An alternative strategy for treatment of new brain metastases is SRS alone initially and WBRT given only to those with treatment failure. Sneed et al.[50] concluded that patients with single metastasis are most likely to benefit from WBRT. However, they noted that SRS without WBRT led to salvage (delayed) WBRT in only 26% of their patients, thus sparing 74% the loss of time, the expense, and the risk of dementia.

Deinsbeger et al.[15] studied 110 patients with new brain metastases and found a local control rate of SRS without WBRT of 89.4% and a median survival of 12.5 months. Based on this high rate of control with the single modality, they recommended that WBRT be reserved for cases of numerous metastases or used in a delayed fashion for recurrence. Conversely, Aoyama et al.[3] found a significantly higher need for salvage WBRT in patients who had undergone SRS alone compared with those treated with SRS and WBRT initially.

Further evaluation is needed to clarify the proper use and timing of WBRT in patients treated with SRS. The North Central Cancer Treatment Group Is currently treating patients harboring one to three brain metastases with SRS alone and with SRS followed by WBRT. Overall survival duration, central nervous system control, quality of life, and toxicity are among the end points. Such data from a large study may help the clinician in the future with this decision.

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