Study: Pausing hormone therapy to pursue pregnancy does not increase the short-term risk of early-stage cancer recurrence
Most relevant for: Women with breast cancer who are considering pregnancy. It may also be relevant for:
- people with breast cancer
Strength of Science: Medium-High
Research Timeline: Post Approval
Why is this research important?
Breast cancer is the most common cancer for women under age 40. Family planning and fertility is often a priority at these ages, and these concerns can affect quality of life and whether patients stay on treatment. Experts typically recommend 5-10 years of hormone therapy after surgery and chemotherapy for breast cancer. To become pregnant, hormone therapy must be discontinued or interrupted. Because fertility decreases with age, delaying conception for 5-10 years to complete hormone therapy may greatly decrease the ability to have children.
Although past research shows that pregnancy after breast cancer does not worsen outcomes, more research is needed to show that it is safe to temporarily stop treatment to become pregnant.
What is the POSITIVE trial?
The POSITIVE trial was an international study designed to learn whether it is safe to interrupt hormone treatment for breast cancer to become pregnant after a recent diagnosis of breast cancer. Birth rates and potential pregnancy complications were also studied.
POSITIVE followed 497 participants under age 42 who interrupted their hormone therapy to try to conceive. Most participants:
- identified most frequently as white.
- were 35-39 years old.
- had 1 or 2 cancer.
- had received chemotherapy in addition to their hormone therapy.
Of the 497 participants, 59 had a known (38 in or BRCA2; the remainder in other genes).
- 368 of 497 participants (68%) had at least one pregnancy.
- Most of the women with successful pregnancies were younger.
- Almost half of the women in the study who became pregnant used some sort of fertility treatment.
- Pregnancy complications and birth defects occurred at rates similar to healthy women of the same age.
- Overall, women who interrupted their breast cancer hormone therapy for pregnancy:
- had no increased risk of breast cancer during the 3 years of follow-up care.
- 9% of women in the group that interrupted treatment were diagnosed with recurring breast cancer. This number was similar to women who did not stop hormone therapy (a different study provided the statistics for the risk of recurrence in women who did not stop hormone therapy).
- Most women with an did not have a cancer recurrence during this study.
- 9 of 59 participants (15%) with an had a recurrence.
- 35 of 457 participants (8%) without a known had a cancer recurrence.
- Because the number of people with mutations and the number of cancer recurrences were small, it is unclear whether women with an had a similar or increased possibility of cancer returning. Additional research is needed to clarify this.
This study followed patients for only three years. Longer follow-up is needed to understand whether these results are similar when more time has passed since the initial diagnosis.
What does this mean for me?
For young, breast cancer survivors who wish to pursue pregnancy, pausing hormone therapy for up to two years while attempting to conceive does not increase the short-term risk of breast cancer returning. During a treatment pause, pregnancies in study participants tended to be healthy and followed breast cancer recurrence trends seen in the general population. Additional research is needed to confirm these results and measure the longer-term risk of cancer returning.
Partridge A, Niman S, Ruggeri M, et al., Interrupting Endocrine Therapy to Attempt Pregnancy After Breast Cancer. The New England Journal of Medicine; 2023; Article number 18. Published online May 4, 2023.
Disclosure: FORCE receives funding from industry sponsors, including companies that manufacture cancer drugs, tests and devices. All XRAYS articles are written independently of any sponsor and are reviewed by members of our Scientific Advisory Board prior to publication to assure scientific integrity.
Share your thoughts on this XRAY review by taking our brief survey.
- What is the risk of my breast cancer recurring?
- Is it safe for me to pause hormone therapy to become pregnant? Is it safe for my baby?
- What screening will I need during and after pregnancy if I pause hormone therapy?
- As a young cancer survivor, what resources are available to help me with family planning?
- How long after pregnancy should I wait before resuming hormone therapy?
The following research studies related to fertility preservation are enrolling patients.
Fertility preservation studies for women
- NCT01503190: The Immune System's Response to Young Women's Breast Cancer. This an observational trial looking at tissue samples from patients with Pregnancy-Associated Breast Cancer (PABC) versus non-PABC to understand how the immune system responds.
- NCT05443737: Evaluation of a Telehealth Oncofertility Care Intervention in Adolescent and Young Adult Cancer Patients. The purpose of this study is to evaluate the effectiveness of an intervention to improve young cancer survivors' oncofertility care.
- NCT0301168: Fertility Preservation Using Tamoxifen and Letrozole in Sensitive Tumors Trial (TALES). Infertility as a result of cancer treatment effects long-term quality of life in survivors of reproductive-age cancers. This trial will study different options for fertility preservation in patients with estrogen-receptor-positive breast cancer.
- NCT00823654: Serum Biomarkers to Characterize the Effects of Therapy on Ovarian Reserve in Premenopausal Women With Breast Cancer or Mutations. This study will look at how cancer treatment affects the ovaries. Researchers will review blood samples before, during and after cancer treatment to look at levels of hormones that are produced by the ovaries and ask patients to fill out questionnaires about their menstrual cycles (periods), overall health and pregnancies.
- NCT01788839: Longitudinal Sexual and Reproductive Health Study of Women With Breast Cancer and . This study looks at how cancer treatment affects sexual and reproductive function. The patient will be asked to give a blood sample to see if and how cancer treatment affects the ovaries and the ability to have children (fertility). These blood draws are optional; patients can participate in the study questionnaire even if they choose not to have their blood drawn.
- NCT01558544: Cryopreservation of Ovarian Tissue. The study hopes to contribute to the development of technologies of ovarian tissue freezing-thawing the preserve fertility. The study is open to women who will undergo treatment or surgery for cancer or women with an who are considering undergoing risk-reducing surgery.
Fertility preservation for men
- NCT02972801: Testicular Tissue Cryopreservation for Fertility Preservation. Testicular tissue cryopreservation is an experimental procedure where testicular tissue is retrieved and frozen. This technique is reserved for young male patients, with the ultimate goal that their tissue may be used in the future to restore fertility when experimental techniques emerge from the research pipeline.
The National Comprehensive Cancer Network (NCCN) provides guidelines for fertility in people diagnosed with cancer.
The NCCN recommends doctors discuss the following with adolescents and adults with cancer before treatment begins:
- fertility plans and preferences
- fertility preservation options, including:
- whether therapy can be delayed long enough for a cycle of egg stimulation
- medications like GnRH agonist therapy during to preserve ovarian function in premenopausal women with breast cancer
- importance of follow-up with a gynecologist or fertility specialist to monitor ovarian function over time
- risks for infertility due to cancer and related treatment
- affects of treatment on breastfeeding
- the importance of avoiding pregnancy and options for safe and effective birth control while in treatment
- safe timing for considering pregnancy after treatment
- emotional impact of discussions about fertility preservation
- financial resources for fertility preservation
- effects of treatment on sexual function during and after treatment
Doctors should refer patients as indicated for the following services:
- All patients who are interested in preserving their fertility should be referred to a fertility preservation clinic before starting treatment.
- Patients who need assistance with complex medical decision-making should be referred to a mental health professional.
- Patients who are experiencing sexual disfunction should be referred to a sexual health specialist.
The following resources can help you locate an expert near you or via telehealth.
Finding fertility experts
- The Oncofertility Consortium maintains a national database of healthcare providers with expertise in fertility preservation and treatment of people who are diagnosed with cancer or at high risk for cancer due to an .
- Livestrong has a listing of 450 sites that offer fertility preservation options for people diagnosed with cancer. Financial assistance may be available to make the cost of fertility preservation affordable for more patients.
Other ways to find experts
- Register for the FORCE Message Boards and post on the Find a Specialist board to connect with other people who share your situation.
- The National Cancer Institute (NCI)-designated comprehensive cancer centers have specialists to manage the fertility effects from cancer prevention or treatment.