First of all, the usual "medical disclaimer". I am not a doctor. This is a question you should pose to the radiation doctor.

Having said that, I can tell you my personal experience.

With you driving and him sitting diagonally in the back seat you are about three feet away from each other. They turn you loose from the Pluvicto administration when your radiation level is around three. Radiation exposure is cumulative so during the two hour drive you are getting about a six - not great but in my opinion nothing to be particularly concerned about.

I live about an hour and a half drive from my treatment center. I too have minimal side effects from the treatment. As such. I drive myself to and from the treatment in order to minimize me exposing anyone else.

After treatment. I completely isolate myself for one week based on my declining radiation levels. They tell you to isolate at least three feet for three days, but I am personally not comfortable that that is sufficient for my tastes. I then restrict my close contact for a second week (no sleeping together, brief hugs or handshakes ok but no prolonged physical contact etc.) After those two weeks my radiation level is negligible so all contact is fair game.

Since your friend also has minimal side effects, is there any reason he couldn't drive himself?