Sorry to hear of your diagnosis . Hopefully , it will be slow growing and you have minimal symptoms .The issue with driving is that the brain tumour puts you at risk of having a seizure or seizures which could put you In danger of an RTA affecting both yourself and possibly others . 

I was diagnosed with metastatic renal cancer with secondaries in my lungs and brain . I am well and the only symptoms I have are due to the side-effects of radiotherapy and my targeted medication ( Sunitinib ) . The cancer is responding well to treatment . I have not had any seizures either .

As I expected the DVLA asked me to return my driving licence . I can reapply for one after two years with evidence that I have had no seizures and the condition is stable . My consultant is required to provide the medical evidence to support this . I'm an active 66 year old . I really miss the independence that driving gave me . I now have to rely on my husband to take me to appointments etc . But you are very young so giving up driving would be an even greater sacrifice .

( I am a retired optometrist who worked within a hospital ophthalmology department . I regularly had to advise patients that their vision did not meet the required standard for driving and that they would need to contact the DVLA ) 

I hope your condition remains stable and good luck . Angela

Thank you for your reply, i guess the positive side is i'll get aIot fitter. I hope your treatment is going well.