Interrupting hormone therapy to conceive

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Fertility preservation for people with cancer > Interrupting hormone therapy to conceive

Clinical Question

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]

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Consensus-based recommendationQuestion mark transparent.png

Limited existing data are reassuring for low-risk breast cancer patients who wish to interrupt hormone therapy to conceive. Health professionals should examine and discuss the current evidence with patients before considering the interruption of treatment to conceive.

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  1. Nye L, Rademaker A, Gradishar WJ. Breast Cancer Outcomes After Diagnosis of Hormone-positive Breast Cancer and Subsequent Pregnancy in the Tamoxifen Era. Clin Breast Cancer 2017 Jul;17(4):e185-e189 Available from:
  2. Taketani K, Tokunaga E, Yamashita N, Tanaka K, Akiyoshi S, Okada S, et al. Early discontinuation of adjuvant hormone therapy is associated with a poor prognosis in Japanese breast cancer patients. Surg Today 2014 Oct;44(10):1841-6 Available from:
  3. Delozier T, Switsers O, Génot JY, Ollivier JM, Héry M, Namer M, et al. Delayed adjuvant tamoxifen: ten-year results of a collaborative randomized controlled trial in early breast cancer (TAM-02 trial). Ann Oncol 2000 May;11(5):515-9 Available from:
  4. Rosenberg SM, Gelber S, Gelber RD, Krop E, Korde LA, Pagani O, et al. Oncology Physicians' Perspectives on Practices and Barriers to Fertility Preservation and the Feasibility of a Prospective Study of Pregnancy After Breast Cancer. J Adolesc Young Adult Oncol 2017 Sep;6(3):429-434 Available from:

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A: Clinical question

B: Body of evidence

C: Literature search

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