Hi,
The effects of both tobacco and marijuana -as well as other chemicals that may cause bladder cancer-take many years to do their damage. People who quit smoking 20 yrs earlier can get bladder cancer. People who never smoked in their life also get it.
I'm sorry to hear that your father's cancer is aggressive, it's a good reason to get surgery. The new tumor could well have been a result of the first operation though, this can happen when tumor cells are dislodged during the TUR.
It's not good to continue to smoke once a person has been deemed a 'cancer friendly environment'. But stress is just as bad. If smoking marijuana is the way your father copes, then perhaps he needs it more than ever at this point. I don't think it will cause the cancer to be any more aggressive than it would be if he didn't smoke, or if he stops now.
Maybe he will stop when the surgery is over and he has a chance to begin adapting to a new life, without cancer.
I don't think he needs to confess to his doctors because I seriously doubt it would make any difference in the way things go.
All the best to you and your father.
Wendy