As always with these sort of things, you either have faith in the establishment or not.

Statistics can prove anything, depending on where you start from, etc. Personal conviction can override that common sense.

However, the establishment (maybe pharma influenced) says that statistically there is no evidence of Vit D helping against cancer.
On the other hand, keeping your Vit D levels up (so long as you don't overdose) is not going to hurt you, and is going to make you healthier. If it also helps against cancer... that is a plus.