Brain metastases are the most common intracranial tumors. The RTOG Recursive Partition Analysis identified several factors and created 3 prognostic classes for brain metastases.
| Class | Description | Median Survival |
|---|---|---|
| I | Age < 65, KPS ≥ 70, primary controlled, no extracranial mets | 7.1 months |
| II | all not class I or III | 4.2 months |
| III | KPS < 70 | 2.4 months |
The prognosis is based on the RPA prognostic classification given above. Spurduto et al. refined the RPA further by segregating prognostic groups based on primary disease lesion. The Graded Prognostic Assessment (GPA) adds the number of lesions (1 v. 2-3 v. > 3) and histopathology in determining outcomes segregating based on NSCLC, SCLC, melanoma, RCC, breast cancer, gastrointestinal cancers and others.
There are a variety of treatment options for a single metastasis. Surgery is frequently used for a single metastasis, particularly where there is signficant mass effect, and there is no histologically proven primary. For assymptomatic patients, the decision depends on the extent of extra-cranial disease and general medical condition. Two randomized studies have shown the benefit of surgical resection followed by whole brain radiation. This benefit was seen in freedom from neurologic progression and overall survival. A third study failed to show a survival advantage with surgery added to whole brain radiation.
Whole brain radiation is based on studies with multiple metastases. Prospective and randomized trials (Phase III) with widely varying fraction have been completed:
No regimen proved superior in terms of survival or effectiveness. About half of the patients had an improvement in their neurological symptoms. Generally the most frequent dose/fraction scheme is 30 Gy in 10 fractions at 3 Gy/fraction or 37.5 Gy in 15 fractions at 2.5 Gy/fraction. These schemes give excellent palliation and in radiosensitive tumors can frequently be used alone. Other may require stereotactic boost.
Data not included in the present ACR criteria originating in Germany give some indications that high dose per day may be problematic. The German study published in the August 2012 NEJM examined toxicity of various dose and fractionation schemes by using comprehensive pre- and post- treatment neurocognitive studies, finding mild problems with doses at or below 3 Gy/fraction-day but increasing toxicities with higher fraction doses. The found no difference between 30 Gy in 10 or 40 Gy in 20. There are some isolated reports that later development of leukoencephalopathy may be more prevalent in higher dose/fraction treatments.
The options studied to date include:
A multi-institutional outcome study demonstrated SRS + WBRT produced the same outcomes as surgery + WBRT.