Monday, October 20, 2025 Pausing endocrine treatment to attempt pregnancy can be considered - no additional risk of recurrences after 5 years. The MAC18 (POSITIVE) study, evaluating the pregnancy outcomes and safety of interrupting endocrine therapy for young women with endocrine responsive breast cancer who desire pregnancy long-term analysis was presented at the European Society for Medical Oncology (ESMO) Congress in Berlin, Germany. The aim of the study was to investigate if temporary interruption of endocrine therapy, with the goal to permit pregnancy, is associated with a higher risk of breast cancer recurrence. The study aims also to evaluate different specific indicators related to fertility, pregnancy and breast cancer biology in young women.Thanks to all of the CCTG sites who participated, making Canada one of the top 10 accruing countries globally and responsible for a quarter of the North American patients enrolled on the trial. As of December 2019 the final international accruals were 518 patients (target: 500) with 29 enrolled patients from Canada.The study was conducted worldwide by the International Breast Cancer Study Group (IBCSG), a division of the ETOP-IBCSG Partners Foundation (the global trial sponsor), in collaboration with the Alliance for Clinical Trials in Oncology (the North American trial sponsor), and with the Breast International Group (BIG). The study concept was initiated within the BIG-NCTN (National Clinical Trials Network) Endocrine Working Group, then developed, and coordinated globally by the IBCSG to address this important, patient-oriented, unmet medical need.
