At long follow-up, roughly one in five women is dissatisfied with a risk-reducing mastectomy. The largest long-term study — 572 women a mean of 14.5 years after bilateral prophylactic mastectomy at the Mayo Clinic — found 19% dissatisfied with the procedure, alongside 74% who reported diminished emotional concern about developing breast cancer (Frost et al., 2000). That dissatisfaction is mostly about the body rather than the decision: about a third reported an unfavourable effect on satisfaction with body appearance, and a quarter on feelings of femininity. An independent Norwegian cohort of BRCA1/2 carriers pins the narrower figure down — only about 7% would not choose the same operation again, though a third said the cosmetic result was not as expected, and lower satisfaction clustered among women who found the decision process difficult or felt unsupported by their clinicians (Hyldebrandt et al., 2025). The regret that exists tends to attach to reconstruction complications and to decisions that felt externally initiated, not to the cancer-risk reduction the surgery reliably delivers.
The surveillance side has no direct regret survey at all, so its rate is a proxy assembled from two things. First, the harm that materialises: in a Canadian cohort, 14% of women who chose surveillance developed breast cancer (9.9% cumulative at five years), against 6% among those awaiting surgery (Macadam et al., 2021). Second, the burden that persists: on the one measure taken comparably on both arms — cancer worry — surgery lowers it and surveillance does not. A prospective cohort found anxiety fell over six to eight months in women who chose mastectomy but rose in women who chose surveillance, ending higher in the surveillance group (Dick et al., 2022). Developing a cancer is not the same as regretting the choice, and many surveillance-detected cancers are caught early, so the 14% inaction figure is a materialised-harm-plus-worry stand-in, not a measured regret rate.
The two numbers land close together, but the closeness is fragile: it depends on which proxy anchors each side. They are not measuring the same thing — the action rate is long-term dissatisfaction with an irreversible operation, while the inaction rate is cancer incidence plus unresolved worry among women who kept their breasts. Swap the broad 19% dissatisfaction for the narrower 7% who would not choose the surgery again, and the balance tips toward surveillance; anchor the inaction side on the 9.9% five-year cumulative incidence instead of the 14% crude rate, and it tips the other way. On the worry axis alone the surveillance side carries more — the Gilovich-typical pattern in which the road not taken keeps generating unease — but risk-reducing mastectomy is permanent and exacts body-image and reconstruction costs that surveillance never imposes, which is what holds the action-side dissatisfaction up to meet it. None of the underlying data is a US survey of the surveillance arm, and no study asks surveillance-choosers directly whether they would decide differently, so the near-balance is a direction with wide error bars, not a settled equivalence.