LOL... this is quite comical. You support abortion because you think a woman has the right to do what she wants with her body (and the body of the child within her), yet you don't think someone who is in severe pain without prospects of a cure has the right to do what they want with their body.
It is not a slippery slope either. Either the patient is able to state they want it, in which case they should be able to or the patient is not able to make the call, in which case that option is off the table. No one other than the individual in question should be able to make the call.