[haldujai]

I can't speak to parent's practice but the cancer centers I've worked at follow the NCCN guidelines (apart from patients enrolled in trials, although this is also a NCCN recommendation) and many cases are reviewed in multi-disciplinary conferences to homogenize practice within an institution.

Although guidelines are just that (i.e. not mandatory to adhere to) I really doubt an oncologist in US/Canada "practices as they please".