Yes, it's almost certainly the comorbidites that are concerning them. They might not want you to end up with kidney failure or a stroke trying to prevent a cancer recurrence that might never happen anyway (or would happen later that the other crises).

Still, it's your life, not theirs. Let the doctors explain the long-term risks and possible interactions with other meds, then state clearly what *you* want and what risks you're willing to accept. I hope you can find common ground, and best of luck!