Many more young breast cancer patients will be seeking medical advice about pregnancy, because oophorectomy is no longer performed adjuvantly, and more women are bearing children in later years. In the meager amount of literature on the topic, it has been observed that breast cancer patients who subsequently become pregnant have as good a survival rate as those with no subsequent pregnancy. In particular the case-matching studies attempt to eliminate the obvious factor of pregnancy occurring only in those with a good prognosis. Survival in cases with subsequent pregnancy is reported in some studies as better than in the controls with no posttreatment pregnancy.
All reports are retrospective, are composed of small numbers of patients, were gathered over several decades, and rely on clinicians' memories, because subsequent pregnancy has not been recorded systematically. For example, the largest study includes 136 patients accumulated over 50 years. Assuming that only a small percentage of fertile breast cancer patients become pregnant, the majority appear to have been “lost to follow-up” and unreported.
In summary, the limited literature on pregnancy subsequent to breast cancer does not allow one to be certain about its effect. Regarding advice to the individual patient who has decided to become pregnant, most clinicians traditionally have recommended a delay of 2 years or more to allow aggressive disease to become manifest.