Lapatinib certainly demonstrated capability to prevent (reduce the risk) of metastases in the results of the phase 3 clinical trial of Xeloda+Lapatinib versus Xeloda alone published in june 2006. (4 cases of brain mets versus 16 among 2 groups of each 120 patients).This trial was not intended for brain cancer,
A clinical trial devoted to treat brain cancer with Lapatinib is currently in phase 2:
http://www.clinicaltrials.gov/ct/gui/show/NCT00098605