Although contralateral breast cancer (CBC) is the most frequent second malignant tumor among women who have experienced a diagnosis of primary breast cancer,¹ it is less frequent, and less ominous than recurrence of the initial cancer. Nevertheless, for many patients with newly diagnosed unilateral breast cancer, it can be a prominent source of worry as they navigate their treatment decisions.² This worry is accentuated among young patients and those with early-stage disease.³ The most effective preventive solution for CBC is contralateral mastectomy, which was rarely used in the 20th century but has been increasingly used during the past 20 years, first in the US,³ and now in other countries with comparable resources.⁴ For women with a unilateral breast cancer, the consideration of contralateral mastectomy has many drivers, some undoubtedly patient-related, but others stemming from misconceptions among the medical community regarding the risks and benefits of contralateral mastectomy.⁴ To date, studies addressing the question of survival following contralateral phylactic mastectomy (CPM) have failed to provide evidence for improved survival.⁵ Although lack of survival benefit may seem counter-intuitive, a tenable explanation is that the dominant hazard to survival derives from the index primary tumor rather than the CBC. Because patients with breast cancer are diagnosed with the index primary tumor at a younger age (which increases the hazard of death) and are treated with older, less effective regimens, it is possible that the risk of death from CBC is subsumed by the risk from the index cancer, particularly if second cancers are diagnosed at earlier stages in survivors who tend to be more adherent to posttreatment screening. Consequently, surgical measures to prevent a second primary tumor do not extend survival.