Pausing endocrine therapy for pregnancy appears safe for women with breast cancer

Pausing endocrine therapy for pregnancy appears safe for women with breast cancer

December 08, 2022

3 min read


Partridge AH, et al. Abstract GS4-09. Presented at: San Antonio Breast Cancer Symposium; Dec. 6-10, 2022.

The researchers’ report no relevant financial disclosures.

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SAN ANTONIO — Young women with early hormone receptor-positive breast cancer who temporarily stopped endocrine therapy to attempt pregnancy experienced similar short-term recurrence risk as those who did not stop, according to study results.

Nearly three-quarters of women who temporarily stopped endocrine therapy had at least one pregnancy and the rate of birth defects was low, findings of the ongoing POSITIVE trial presented at San Antonio Breast Cancer Symposium showed.

Infographic with quote from Ann H. Partridge, MD, MPH

Background and methods

Standard endocrine therapy may reduce ovarian reserve and decrease the likelihood of subsequent successful pregnancy.

In addition, conception is contraindicated during endocrine therapy, according to study background.

A temporary interruption of endocrine therapy to allow women in this population to attempt and carry a pregnancy has never been prospectively studied, according to Ann H. Partridge, MD, MPH, vice chair of medical oncology and director of the adult survivorship program at Dana-Farber Cancer Institute, and colleagues.

“There is a strong desire from many of our patients to have children after cancer and receive best breast cancer treatment, but adjuvant hormonal therapy for these women poses a real dilemma in this regard,” Partridge told Healio.

As Healio previously reported, the POSITIVE trial aims to assess safety and pregnancy outcomes of interrupted hormonal therapy among a cohort of young women with breast cancer.

The prospective, nonrandomized trial includes 518 premenopausal women (median age, 37 years; 75{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} nulliparous; 93.4{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} stage I to stage II disease; 66.3{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} node-negative disease) with a desire to become pregnant.

Researchers recruited women from 116 centers across 20 countries, including 61{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} in Europe, 23{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} in North America, and 16{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} in Asia/Pacific and Middle East nations.

All participants completed 18 to 30 months of adjuvant endocrine therapy before pausing treatment.

A data safety monitoring committee conducted three interim safety analyses. Researchers set a trial suspension threshold of 47 or more breast cancer recurrences that occurred within 3 years of median follow-up.

Breast cancer-free interval, defined as time from enrollment to first breast cancer event, served as the primary endpoint.


At median follow-up of 41 months, results showed 44 women experienced breast cancer recurrence, corresponding to a 3-year recurrence rate of 8.9{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} (95{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} CI, 6.3-11.6). This appeared comparable to the 9.2{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} rate (95{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} CI, 7.6-10.8) observed in a comparative external control cohort from the SOFT/TEXT trials.

Overall, 368 women (74{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547}) had at least one pregnancy and 317 women (64{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} of all women; 86{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} of those who became pregnant) had at least one live birth.

Among the 365 babies born, researchers reported 8{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} as low birth weight and 2{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} with birth defects.

Results of competing risk analysis at 48 months follow-up showed the majority (76.3{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547}) of women resumed endocrine therapy after pregnancy attempt or success, 8.3{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} experienced a breast cancer-free interval event/death before resuming therapy, and 15.4{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} had not resumed therapy.

“Of note, 79{a0ae49ae04129c4068d784f4a35ae39a7b56de88307d03cceed9a41caec42547} of women who were disease-free at 2 years who had not yet resumed endocrine therapy at data lock reported continuing pursuit of pregnancy after a recent pregnancy or breastfeeding at most recent follow-up,” Partridge said.

Researchers acknowledged study limitations. These included short follow-up, as hormone receptor-positive breast cancer can recur many years after initial diagnosis.


Future research will entail longer follow-up of study participants, assessment of the babies’ health, analysis of the psychosocial health of the women who did and did not become pregnant on the trial, and evaluation of several other secondary study outcomes, Partridge said.

“Temporary interruption of endocrine therapy for pregnancy does not appear to negatively impact breast cancer outcomes in relatively short-term follow-up for ER-positive disease,” Partridge told Healio. “Our findings were not particularly surprising but important prospective confirmation of what we have seen in retrospective data. These data stress the need to incorporate patient-centered reproductive health care in the care of young women with breast cancer.”

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