I believe there was a study done for ovarian cancer, treating people whose CA 125 was up but no physical evidence of recurrence, comparing them with people who were not treated until there was physical evidence. Treating early on the basis of CA 125 did not help, at least in terms of mortality. Counterintuitive, but OC seems to be very tricky.
So that's probably why nobody wants to start aggressive treatment on the basis of rising CA 125. The doctors don't want to trade good months where you're physically feeling okay, for bad ones when you're beat up by chemo, if the outcome is no different. I think they don't take into account the misery of knowing something's wrong and not having anything to do about it. I think if this happens to me (I'm in remission right now) I will take myself to a beach or jungle resort before the next scan.