Interrupting hormone therapy to conceive

Does interrupting adjuvant hormone therapy to conceive increase the risk of cancer recurrence for women with a history of breast cancer?

While the importance of endocrine therapy after treatment for hormone responsive breast cancer is well established, little is known about the risk of cancer recurrence for women who interrupt endocrine therapy in order to become pregnant.

One study of pre-menopausal women with estrogen receptor positive breast cancer who became pregnant within five years of their diagnosis found that there was no difference in breast cancer recurrence compared to women who did not become pregnant. There was a significant reduction in the length of time the pregnant women received adjuvant endocrine therapy compared to controls. The numbers of patients and the retrospective nature of this study means that more evidence is needed before conclusions can be made.^[1]

Some studies have identified that a younger age is one of the major factors associated with early discontinuation of endocrine therapy^[2] and others have indicated that starting adjuvant endocrine therapy as late as two years after treatment improves survival.^[3] Results from the "Pregnancy Outcome and Safety of Interrupting Therapy for Women With Endocrine Responsive Breast Cancer (POSITIVE)" clinical trial are pending and should provide an indication of the impact of interrupting hormone therapy on survival for pre-menopausal breast cancer patients.^[4]