My guess is that most people do not have a new biopsy after drugs stop working. Insurance probably doesn't usually pay to have DNA sequencing done twice. (I'm having trouble getting them to pay once.) So even if people do have a reversion of a BRCA2 mutation, they mostly wouldn't know.

It sounds to me like you have an unusually thorough doctor who is making well-informed decisions. Are you concerned that something is wrong? Do you have the sequencing report?