I suspect those treating you would have an obligation to notify the DVLA, if and only if they felt it was likely to impact on your ability to drive. 

As I'm ultra cautious when it comes to motor insurance, if it was me I'd run it past them and see what they say. If they say fine unless or until your are told not to drive by the DVLA then so long as you feel happy to drive you are covered.

i hope that helps a little.

Hello Lilac 

I am so sorry about your recent diagnosis. I think maybe you are reacting to your situation in a panic . Why don't you write everything down that you are concerned about then fold up the paper and visit it again tomorrow . I found when I had my cancer the best thing for me was not to  Google and coming off all social media groups that related to it . We are all different but that helped me tremendously. Also have a list ready for you on the phone appointments I have never liked these kind of appointments and are I think unnecessary under these situations . You will find people helpful and very kind here . 
You are probably in a bit of shock right now but it will calm down and things will start to happen . I wish you a speedy recovery . Love Ginny x x. X

PS I maybe wrong thinking your tumor is cancer it could of course be benign x x x