Brain metastasis

Epidemiology
Far more common than primary brain tumors, up to 100,000 cases per year and increasing
Most common primary sites are lung and breast

Clinical
Majority of patients have headache and/or neuro deficit

RTOG RPA classification (PMID 9128946)
Class I: All of: age less than 65, KPS higher than 70, controlled primary, brain is only site of metastatic disease; OS 7mos
Class II: Everyone who is not in Class I or Class III; OS 5 mos
Class III: KPS less than 70; OS 2 mos

Trials
1) WBRT +/- surgery (PMID 2405271) in patients with single brain mets: Adding surgery to WBRT had local control and overall survival benefit

2) Surgery +/- WBRT (PMID 9809728) in patients with single brain mets: Adding WBRT improved intracranial control (70 vs 18%), decreased rate of neurologic death, but had no impact on overall survival (pts still died of systemic disease)

3) WBRT +/- SRS (RTOG 9508, PMID 15158627) in patients with one to three brain mets: Adding SRS improved local control in all patients (80 vs 70%) but did not affect OS.  Results of the planned subgroup analysis did show a survival benefit to SRS in patients with a single brain met.  Post hoc (unplanned subgroup) analysis also suggested a survival benefit in patients with NSCLC, RPA class I, tumors > 2cm.  No increased toxicity was seen with the addition of SRS.

4) SRS +/- WBRT (PMID 16757720) in patients with one to four brain mets: Adding WBRT improved local control without affecting overall survival.  Companion neurocognitive analysis showed that tumor control was the most important factor predicting for neurocognitive outcome.  (PMID 17674975)

SRS Dosing (based on RTOG 9005, PMID 10802351)
Less than 2cm: 20Gy
Between 2 and 3cm: 18Gy
Between 3 and 4cm: 15Gy
Larger than 4cm: SRS is probably a bad plan