Oleandrin is a single compound, and is considered the primary cardiac glycoside among several contained in oleander. Here is the best information I have regarding indications that other compounds within oleander help transport oleandrin across the blood-brain barrier:
I would suggest that you may want to look at possible faster acting initial therapies for someone who has only weeks left. Oleander typically takes time to work. It would be a good idea in my opinion, but perhaps in conjuction with something like Cesium Chloride or ozone therapy. I would also suggest plentiful curcumin, such as the highly bioavailable Super Bio-Curcumin from Life Extension Foundation. In addition to being a powerful cancer fighter, curcumin is also a good natural anti-inflammatory, an important consideration when dealing with brain cancers.