Results from the POSITIVE clinical trial found that temporarily pausing endocrine therapy to attempt pregnancy in patients with early-stage hormone-receptor-positive (HR+) breast cancer did not lead to greater short-term risk of recurrence, compared with patients who did not interrupt treatment.

Primary results from the study were presented on December 8 at the 2022 San Antonio Breast Cancer Symposium by lead author Ann Partridge, MD, MPH, Dana-Farber Cancer Institute, Boston, Massachusetts.

Dr Partridge stated, “Forty 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.” The study authors also noted only 5% to 10% of this patient population go on to become pregnant after treatment with endocrine therapy.

The single-arm, prospective, international POSITIVE trial was designed to examine the impact of pausing endocrine therapy to pursue pregnancy. The study enrolled 518 women aged 27 to 43 who had received 18 to 30 months of endocrine therapy from December 2014 to December 2019. Data from previous SOFT/TEXT trials, which examined adjuvant endocrine therapy in premenopausal women, were used as an external control cohort. The 2 most commonly prescribed endocrine therapies in the study were tamoxifen alone and tamoxifen plus ovarian function suppression (41.7% and 35.7%, respectively). Additionally, 62% of patients had previously received some form of neoadjuvant or adjuvant chemotherapy. The primary end point of the study was breast cancer free interval, defined as the time between enrollment and the first breast cancer event.

After a median follow-up of 41 months, 44 patients experienced a recurrence, which was less than the predefined safety threshold of 46. The 3-year recurrence rate was 8.9% (95% confidence interval [CI], 6.3% to 11.6%), which was statistically similar to the recurrence rate of 9.2% (95% CI, 7.6% to 10.8%) observed in the SOFT/TEXT trial cohorts.

Of the 518 enrolled patients, the study followed 497 for pregnancy status. Within that group, 368 patients (74%) had ≥1 pregnancy, and 317 (63.8%) had ≥1 live birth. Overall, a total of 365 babies were born in this patient set.

After pregnancy, patients were strongly recommended to resume endocrine therapy. At the time of data cut-off, 76.3% of patients had resumed endocrine therapy, 15.4% had not yet resumed endocrine therapy, and 8.3% had a recurrence or death before restarting endocrine therapy.

While the study authors noted that further investigation is necessary to confirm long-term safety, Dr Partridge concluded, “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.

Source:

Partridge A, Niman S, Ruggeri M. “Breast cancer patients who interrupted endocrine therapy to pursue pregnancy did not experience worse short-term recurrence rates.” Presented at San Antonio Breast Cancer Symposium; December 6 – 10, 2022; San Antonio, Texas. Abstract GS4-09