ADT stands for androgen deprivation therapy, which is another name for hormone therapy (or HT). The usual starting place for ADT is a four week course of tablets (bicalutamide) followed by either monthly or three monthly injections of a drug which stops the production of testosterone. If testosterone is stopped prostate cells become dormant. ADT costs the NHS about £1000 per year.
Enzalutamide (Enzo) is a top of the range drug. I think it costs about £30,000 a year, so usually the NHS held this back as the last treatment.
Thanks to covid men are getting enzalutamide instead of chemo, it is probably the better treatment. Hopefully it will carry on working for a number of years, and then if (when) it stops working they will try one of the other treatments.
I don't know if anyone knows if in the long term starting with Enzo and then switching to the cheeper treatments will prolong life overall, as until covid no one has tested this approach of doing things backwards. Chemo suppresses the immune system so at present it is too risky.
By the time Enzo stops working hopefully covid will be a distant memory and they can then try him on chemo or ADT.
So yes as one treatment fails they will switch to another one. He could probably apply for a trial of a new treatment, once things get desperate, that is a gamble but when you have nothing to loose, so what.
I can understand you wanting to see the consultant with him, and it would be a good idea. But I can see that a man may not want to talk about erections and sexual function, blood in semen, with his daughter in the room, and those topics do come up when dealing with prostate cancer.
You may be able to come to an arrangement where you go to the consultation and agree to leave and wait outside the consultation after a few minutes and then be called in for the summing up. I have never tried this sort of arrangement myself.
How old is your dad? I tend to take the view that if a man reaches 80 he has reached a reasonable age, and PCa is better than alzheimers. If he is under 70 he has been short changed in life and anywhere between 70 and 80 it's a bit of bad luck.
Good luck. if I have missed anything important I hope another contributor will come along. Keep posting on here with any questions, or just to let us know how you are getting on and how he is getting on.