Breast cancer

Women can safely pause endocrine therapy to pursue pregnancy

Prof Ann Partridge

Younger women with breast cancer can safely interrupt endocrine therapy to try to get pregnant and have good pregnancy outcomes, according to results presented at the San Antonio Breast Cancer Symposium.

Findings from the prospective POSITIVE clinical trial showed that women who paused endocrine therapy for around two years experienced short-term rates of breast cancer recurrence similar to women who did not pause therapy for pregnancy, and many went on to conceive and deliver healthy babies.

Study investigator Professor Ann Partridge, vice chair of medical oncology at Dana-Farber Cancer Institute, told the SABCS meeting that about 5% of new breast cancer diagnoses each year occur in women aged 40 or younger, and women with early-stage hormone receptor (HR)-positive breast cancer are often treated with endocrine therapy, such as ovarian function suppression, aromatase inhibitors, or selective oestrogen receptor modulators.

While some retrospective studies have shown that pregnancy after cancer is feasible and safe, many women are concerned that breast cancer treatment will make it difficult to conceive or that pregnancy might exacerbate a woman’s cancer, she said.

To investigate this issue, the single-arm Pregnancy Outcome and Safety of Interrupting Therapy for Women with Endocrine Responsive Breast Cancer  (POSITIVE) trial, enrolled 518 women aged 42 or younger who had completed between 18 and 30 months of adjuvant endocrine therapy and would opt to pause endocrine therapy for approximately two years to try to get pregnant.

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

Of 497 women followed for pregnancy status, 368 (74%) had at least one pregnancy, and 317 (63.8%) had at least one live birth, with a total of 365 babies born.

These rates of conception and childbirth were on par with or higher than rates in the general public, the study investigators said.

Trial participants were strongly recommended to resume endocrine therapy after a pregnancy attempt or success and 76.3% had since resumed their therapy.

The study investigators said the results provided encouraging guidance to younger women diagnosed with breast cancer who may be hoping to have children.

“The POSITIVE Trial provides important data to support young women with HR-positive early breast cancer who are interested in a pregnancy and taking a break from endocrine therapy to pursue one,” said Professor Partridge, who led the study in North America on behalf of the Alliance for Clinical Trials in Oncology.

“Pregnancy after breast cancer is a very personal decision for which, ideally, a woman should take into account not only her desire to carry a pregnancy, but her baseline fertility, prior and current treatment, and any fertility preservation strategy she may have pursued, as well as the underlying risk of cancer recurrence she faces,” said co-investigator Prof Olivia Pagani, the international study chair on behalf of the International Breast Cancer Study Group.

The researchers are continuing to follow the study participants to assess recurrence risk over time. They noted that the short follow-up to date is a limitation of the POSITIVE study, as HR-positive breast cancer can recur many years after an initial diagnosis.

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