Azra,
As I understand it (and I'm not doctor, so I could be wrong) but part of the indicators of using radiation for treatment is size (typically 2cm and smaller). I've HEARD of them using it on larger ones, but quite honestly don't know that much about it. But, the other indicator is location... Especially given that the tumor is already putting pressure on the brainstem pretty badly, that would seem to me to contraindicate radiation (that is to say that it wouldn't be considered).
I say that because with radiation, there is an expectation that the tumor may, in fact, swell larger before it potentially shrinks and dies. Given that it's already putting pressure on the brainstem, I would expect with known swelling as a very real posibility, radiation would not be used as a treatment course.
Something to discuss with the radiation doctor, anyhow..
Good luck!
Regards,
Brian