Multinational prospective trial of interrupting breast cancer endocrine therapy for pregnancy: updated results of POSITIVE

The multinational prospective POSITIVE trial (‘pregnancy outcome and safety of interrupting therapy for women with endocrine responsive breast cancer’) showed that temporary interruption of adjuvant endocrine therapy (ET), after 18-30 months and for up to 2 years, to attempt pregnancy in young breast cancer (BC) patients was feasible and safe at early follow-up (median 41 months). Preplanned analysis with 2.5 years of additional follow-up has now been published. Among 518 participants with stage I-III BC (aged ≤ 42 years at enrollment; median follow-up 71 months), the 5-year cumulative incidence of breast cancer-free interval (BCFI)-events was 12.3% and the 5-year incidence of distant recurrence-free interval (DRFI) events was 6.2%, both outcomes not significantly different from the results of the SOFT/TEXT trials (13.2% and 8.3%, respectively). Among 497 women followed for non-disease outcomes, 377 (76%) had at least one documented pregnancy. The authors conclude that longer-term follow-up of the POSITIVE trial demonstrates that temporary interruption of ET for pregnancy does not increase risk of BC events (graphical abstract).