The tower ending is definitely a permanent choice, no going back once you commit. Surgery removes the relic but puts v in a 2-year coma, and when they wake up everything's different. Can't use cyberware anymore, relationships with panam and others are completely changed, and the merc life is basically over. All those other endings you might've been thinking about get locked out permanently since the timeline jumps forward and v's whole situation is different. Nice survival outcome sure, but there's no way to undo those major life changes once the surgery's done. The story basically closes that chapter for good with all those relationship changes and physical limitations being permanent, so maybe think it through before making that choice

Remember though, if you're still early in the storyline you can always make a backup save before the big decision, just to keep your options open. The game autosaves at key points but having your own save file right before is always smart