Don't be soft in the head.
The issue isn't the cost, the issue isn't availability. The parents want an unproven treatment rather than a proven treatment regime based on what they've read online.
New medical techniques are always unproven for a while, aren't they? How does an unproven treatment become proven? After it's been used for a while? You can only go so far with rats and monkeys.
Anyway, today it's true to say that a lot of info is freely available on the 'net, and you don't need to be a surgeon or doctor to have access to the results of numerous studies. Like this one?
http://www.hccnevada.com/mayo-study...over-imrt-for-advanced-head-and-neck-cancers/