I did like the part where Brian asked the Doctor a very pointed question about what happens to his companions and the Doctor gave him an honest answer.
Looking into his previous Companions, the various Doctors have had 2 deaths (
Adric and
Katarina) out of the 44 Companions who have had more than 1 adventure with him, so what he says is true, that they very rarely die.
I'm not sure how to count River, since she got downloaded to a computer to live her 'life' out, much like the android Kamelion and Jack got better.