Abstract PS12-17: Baseline characteristics of women enrolled in the POSITIVE trial (pregnancy outcome and safety of interrupting therapy for women with endocrine responsIVE breast cancer)

Background: Pregnancy is a major concern for young breast cancer (BC) survivors. Conception after BC in women with hormone receptor positive (HR+) disease is affected by the standard 5-10 years of adjuvant endocrine therapy (ET) during which pregnancy is contraindicated and fertility may be waning. The POSITIVE Trial (IBCSG 48-14/BIG 8-13/Alliance A221405/NCT02308085) investigates the impact of temporary ET interruption to allow pregnancy. Methods: POSITIVE enrolled premenopausal women with stage I-III HR+ early BC, ≤42 years of age, who had received adjuvant ET (SERM alone, ovarian function suppression (OFS) plus SERM or AI) for 18 to 30 months, and wished to interrupt ET to attempt pregnancy. An interruption of ET for up to 2 years was foreseen to allow pregnancy (after a 3-month ET washout period), delivery, and breastfeeding if desired/feasible. Resumption of ET to complete 5-10 years of treatment was planned as soon as pregnancy/breastfeeding was completed or after it was ensured conception was not possible. We report baseline characteristics of participants enrolled in POSITIVE by region of enrollment. Results: From 12/2014 to 12/2019, 518 participants were enrolled at 116 centers in 20 countries across 4 continents. The table shows the baseline characteristics of the enrolled women. Several differences were seen across regions: A higher proportion of participants Conclusion: Regional variation of baseline characteristics of women enrolled in the POSITIVE trial may provide important insights into different medical and sociocultural attributes and attitudes of the study participants and investigators from those regions. Affiliation: POSITIVE Investigators, International Breast Cancer Study Group, Alliance for Clinical Trials in Oncology, Breast International Group, North American Breast Cancer Group Citation Format: Ann H Partridge, Samuel M Niman, Monica Ruggeri, Fedro A Peccatori, Hatem A Azim, Jr, Marco Colleoni, Cristina Saura, Chikako Shimizu, Anna Barbro Saetersdal, Judith Kroep, Ellen Warner, Virginia F Borges, Andrea Gombos, Akemi Kataoka, Christine Rousset-Jablonski, Simona Borstnar, Hideko Yamauchi, Jeong Eon Lee, Janice M Walshe, Manuel Ruiz Borrego, Halle CF Moore, Christobel Saunders, Fatima Cardoso, Snezana Susnjar, Vesna Bjelic-Radisic, Karen L Smith, Martine Piccart, Larissa A Korde, Aron Goldhirsch, Richard D Gelber, Olivia Pagani. Baseline characteristics of women enrolled in the POSITIVE trial (pregnancy outcome and safety of interrupting therapy for women with endocrine responsIVE breast cancer) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS12-17.