Patients With Breast Cancer Who Interrupted Endocrine Therapy to Pursue Pregnancy Did Not Experience Worse Short-Term Recurrence Rates

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Patients with breast cancer who paused their endocrine therapy while attempting to conceive experienced short-term rates of breast cancer recurrence similar to patients with breast cancer who did not pause their therapy for pregnancy—and many of them went on to conceive and deliver healthy babies, according to new findings presented by Partridge et al at the 2022 San Antonio Breast Cancer Symposium (Abstract GS4-09).


While breast cancer is most commonly diagnosed in individuals who are over 40 years, in the United States, about 5% of new diagnoses each year occur in those who are under 40 years. These younger patients may face some unique considerations, including fertility.

“Forty percent to 60% of patients who are diagnosed with breast cancer at age 40 or younger are concerned about their future fertility, especially if the disease occurs before they could decide whether to become a mother or not,” explained lead study author Ann Partridge, MD, MPH, Professor of Medicine at Harvard Medical School and Vice Chair of Medical Oncology at the Dana-Farber Cancer Institute.

Researchers noted that only about 5% to 10% of younger patients with breast cancer may go on to become pregnant. While some retrospective studies have shown that pregnancy after cancer is feasible and safe, many patients are concerned that breast cancer treatment will make it difficult to conceive or that pregnancy might exacerbate their cancer.

Study Methods and Results of the POSITIVE Trial

Young patients with early-stage hormone receptor–positive breast cancer may often be treated with endocrine therapy—such as ovarian function suppression, aromatase inhibitors, or selective estrogen receptor modulators. To examine the impact of pausing endocrine therapy to pursue pregnancy, researchers designed the single-arm POSITIVE (Pregnancy Outcome and Safety of Interrupting Therapy for Women with Endocrine Responsive Breast Cancer) clinical trial. From December 2014 through December 2019, researchers enrolled 518 patients under 43 years—who desired to become pregnant—in the study. The patients opted to pause endocrine therapy for approximately 2 years to try to get pregnant following the completion of 18 and 30 months of adjuvant endocrine therapy.

A data safety monitoring committee conducted three interim safety analyses, and determined that if there were more than 46 breast cancer recurrences within approximately 3 years of average follow-up, the trial would have been suspended. That threshold was not reached.

At a median follow-up of 41 months, 44 participants had experienced a recurrence of breast cancer. The 3-year rate of recurrence was 8.9%, similar to the 9.2% rate in an external control cohort from the SOFT/TEXT trials—which examined adjuvant endocrine therapy in premenopausal patients.

Of the 497 patients followed for pregnancy status, 74% of them (n = 368) had at least one pregnancy, and 63.8% (n = 317) had at least one live birth, with a total of 365 babies born. The researchers discovered that the rates of conception and childbirth were on par with, or higher than, rates in the general public.

Following their pregnancy attempts or successes, the trial participants were strongly recommended to resume endocrine therapy. To date, 76.3% of the patients have resumed their therapies. Dr. Partridge and her colleagues gathered that the study provided encouraging guidance to younger patients diagnosed with breast cancer who may be hoping to have children, though any such decisions should be made in close consultation with health professionals.


“The POSITIVE trial provides important data to support young [patients] with [hormone receptor]-positive early breast cancer who are interested in a pregnancy and taking a break from endocrine therapy to pursue one,” highlighted Dr. Partridge. “Pregnancy after breast cancer is a very personal decision for which, ideally, [patients] should take into account not only [their] desire to carry a pregnancy, but [their] baseline fertility, prior and current treatment, and any fertility preservation strategy [they] may have pursued, as well as the underlying risk of cancer recurrence [they] face,” Dr. Pagani concluded.

The researchers plan to continue following-up with the study participants to assess recurrence risk over time.


Disclosure: The research in this study was supported globally by the National Cancer Institute, Canadian Cancer Society, Canada Foundation for Innovation, RETHINK Breast Cancer, Gilson Family Foundation, International Breast Cancer Study Group, Frontier Science & Technology Research Foundation Southern Europe, Breast International Group against breast cancer and Baillet Latour Fund, Pink Ribbon Switzerland, Swiss Cancer League, San Salvatore Foundation, Rising Tide Foundation for Clinical Research, Swiss Cancer Research Group, Clinical Cancer Research Foundation of Eastern Switzerland, Gateway for Cancer Research, Breast Cancer Research Foundation, Roche Diagnostics International, Swiss Cancer Foundation, Piajoh Fondazione di Famiglia, Gruppo Giovani Pazienti “Anna dai Capelli Corti,” Verein Bärgüf, Schweizer Frauenlauf, C&A, Dutch Cancer Society, Norwegian Breast Cancer Society, Pink Ribbon Norway, ELGC K.K. Japan, Pink Ring Japan, Korea Breast Cancer Foundation, as well as Yong Seop Lee and other donors.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.