I am pretty sure that my dog Lucky developed the tumor because of one of the vaccinations she received - however, I can honestly not be 100% sure.
I take Lucky on vacation with me, and one of the requirements of the B&B I go to is that all shots are up to date. This time around they are not, as we stopped them when she was diagnosed with cancer. Lucky was never fragile so I somehow doubt that's the reason why some dogs get sick and others don't.
Most of the vaccinations are really only important if you put your dog into a kennel or a similar situation.
I let Lucky roam around quite a bit (there are a number of off-leash woodsy parks in the area) so I always wanted her to have the Rabies vaccination - the risk just seemed too high.
On the other hand it is horrible to receive the news that your dog has terminal cancer. I think if you can avoid the shots, avoid them.