Updated results of the POSITIVE (Pregnancy Outcome and Safety of Interrupting Therapy for Women with Endocrine Responsive Breast Cancer) trial.

BACKGROUND

In patients with hormone receptor (HR)-positive early breast cancer (BC), the POSITIVE trial demonstrated that temporary interruption of adjuvant endocrine therapy (ET) for pregnancy is feasible and safe in early follow-up (median 41 months). In this article, we report updated results from a preplanned analysis with 2.5 years of additional follow-up.

PATIENTS AND

METHODS

POSITIVE, a single-arm prospective trial evaluating temporary interruption of adjuvant ET (after 18-30 months and for up to 2 years) to attempt pregnancy in young patients with BC, enrolled 518 eligible women (≤42 years of age, stage I-III BC, desiring pregnancy) from December 2014 to December 2019. Using the bootstrap-matching method, 5-year breast cancer-free interval (BCFI) and distant recurrence-free interval (DRFI) event rates were compared with those of the SOFT/TEXT trials as external controls.

RESULTS

At a median follow-up of 71 months in the POSITIVE cohort and 80 months in the SOFT/TEXT cohort, the 5-year cumulative incidence of BCFI events was 12.3% in POSITIVE and 13.2% in SOFT/TEXT [-0.9% difference, 95% confidence interval (CI) -4.2% to 2.6%]. The 5-year cumulative incidence of DRFI events was 6.2% and 8.3%, respectively (-2.1% difference, 95% CI -4.5% to 0.4%). Among 497 women followed for nondisease outcomes, 377 (76%) had ≥1 documented pregnancy on trial, and 343 of 497 (69%) had ≥1 live birth, totaling 440 offspring. In an unadjusted analysis comparing the 180 women (36%) who had pre-enrollment embryo/oocyte cryopreservation with those who did not, the 5-year cumulative incidence of BCFI events was 14.0% (95% CI 9.6% to 20.2%) and 11.5% (95% CI 8.4% to 15.7%), respectively.

CONCLUSION

Longer-term follow-up of the POSITIVE trial demonstrates that temporary interruption of ET for pregnancy, including use of fertility preservation, does not increase the risk of BC events. Continued follow-up is warranted given the known risk of late recurrence in this population.