JBCRG Announces Publication of 71-Month Follow-Up Results of POSITIVE Trial in Annals of Oncology

The Japan Breast Cancer Research Group (JBCRG) (Representative Director: Shigekazu Saji, located in Chuo-ku, Tokyo) announced that the 71-month follow-up analysis results of the international collaborative clinical trial "POSITIVE trial (Pregnancy Outcome and Safety of Interrupting Therapy for Women with Endocrine Responsive Breast Cancer)" in which the organization participates, have been published in the international academic journal Annals of Oncology. This trial examined the safety of interrupting endocrine therapy and subsequent pregnancy in young patients with hormone receptor-positive breast cancer.

*1 The POSITIVE trial is a large-scale international collaborative study conducted in 20 countries across Europe, North America, Asia Pacific, and the Middle East, under the leadership of the non-profit research foundation ETOP IBCSG Partners Foundation based in Switzerland, in collaboration with the Breast International Group and the Alliance for Clinical Trials in Oncology. As a member of the Breast International Group, JBCRG is responsible for the planning and management of the POSITIVE trial in Japan.

https://jbcrg.jp/topics/1981/

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■ Background of the Study

In recent years, along with the increase in young breast cancer patients and improved prognosis due to treatment advances, the medical need for patients who wish to become pregnant and give birth after cancer treatment has been growing.

Particularly in hormone receptor-positive breast cancer, long-term (5-10 years) postoperative endocrine therapy is recommended to prevent recurrence, and contraception is required during treatment, making the timing of pregnancy a major challenge.

The POSITIVE trial is the world's first large-scale international collaborative study to prospectively evaluate the safety of temporarily interrupting postoperative endocrine therapy to attempt pregnancy.

■ Current Announcement (71-Month Follow-Up)

This study analyzed long-term follow-up data of 71 months (approximately 6 years) in addition to previously reported short-term results.

The main results are as follows:

◇ No clear increase in long-term breast cancer recurrence risk was observed by temporarily interrupting endocrine therapy to attempt pregnancy.

◇ Pregnancy and childbirth outcomes remained favorable, with more than two-thirds of participants achieving live births.

◇ Among the 36% of participants who underwent fertility preservation therapy (oocyte cryopreservation/embryo cryopreservation) before enrollment, there was no increase in recurrence risk.

■ Significance of the Study

These results provide:

・ Scientific evidence supporting the important option of "balancing treatment and pregnancy" for young breast cancer patients

・ Insights that can influence clinical guidelines and decision-making in clinical practice

This is positioned as one of the first high-quality data demonstrating long-term safety in an area where cautious judgment was previously required due to a lack of evidence.

■ Paper Information

Title: Updated Results of the POSITIVE (Pregnancy Outcome and Safety of Interrupting Therapy for Women with Endocrine Responsive Breast Cancer) Trial

Journal: Annals of Oncology

Publication Date: May 28, 2026 (Online publication)

Link: https://authors.elsevier.com/sd/article/S0923-7534(26)00883-5

■ Role of JBCRG

JBCRG contributed to patient participation and research promotion from Japan in the POSITIVE trial, contributing to the generation of evidence for young Japanese breast cancer patients. Additionally, JBCRG promotes research activities aimed at expanding treatment options and improving the quality of life (QOL) for young breast cancer patients.

■ Future Outlook

Going forward, JBCRG aims to:

・ Conduct further follow-up to confirm long-term safety

・ Conduct research to elucidate the nature of young breast cancer

・ Build scientific treatment strategies for young breast cancer patients through research on the biological effects of pregnancy on breast cancer

■ About JBCRG

The Japan Breast Cancer Research Group (JBCRG) is a research group that aims to improve patient prognosis and quality of life (QOL) through the promotion of clinical research on breast cancer. Particularly in the field of young breast cancer, JBCRG is working to create new evidence that supports the balance between treatment and life events, contributing to the expansion of treatment options for each patient.

As part of these efforts, JBCRG will host the international conference "The 3rd International Conference on Young Women's Breast Cancer and Health (YWBCH 2026)" in Tokyo on November 14 and 15, 2026. This conference will share cutting-edge knowledge, including international research results like the POSITIVE trial, and will be a valuable opportunity for domestic and international experts to gather.

▼ Details: https://procomu.jp/ywbch2026/