I don't believe there is a way to stop speaking with your family. That they will not ask questions about it all over the years. Parents and loved ones have always done this regardless of circumstances. They could feel that they could have stopped it, done better, turned things around, not run you off, and other related issues.
However if you feel the need to cut contact? If it is because they are like my parents? They view you as a sin, something that is insane, and once again other related things? You should cut them off in a way you won't regret. Besides that? Do it soon because the longer you wait the harder it will be even if they are worthless parents.
Now if you love them and they you? The relationship is positive? I have to wonder why you'd wish to cut ties? Do they nitpick? Always use the wrong pronouns? Take jabs when they can about your choice? Support you but still treat you almost poorly with verbal comments and other life issues? Even if it is positive if they are treating you poorly like this? Then it is unhealthy for you and it will be extremely hard to let go I'd imagine. Its killing me in ways and my bother is the above lousy parent. But since it is unhealthy for you? And you know they are not going to change on it? Do something once again you won't regret but let them know why you made the choice in a calm manner. A way that maybe someday? You can at least see them before they pass on.
I doubt I will get to see mine or even know where she is after I leave. Even on her deathbed I will likely not know where she is or that she is on it. Make the choice carefully if you can.