This trial evaluates the pregnancy outcomes and safety (in term of disease relapse) of interrupting adjuvant endocrine therapy for young women with ER+ breast cancer who wish to become pregnant.

Young women with breast cancer are a significant part of the overall breast cancer population 

• About 20% of patients with breast cancer are diagnosed during their reproductive years
• In recent decades, women have tended to delay childbearing, so increasingly, breast cancer occurs before they have completed their families.
• The majority of young women with early breast cancer have hormone receptor positive (HR+) disease.
• Forty to 60 percent of patients who are diagnosed with breast cancer at age 40 or younger are concerned about their future fertility, especially if the disease occurs before they could decide whether to become a mother or not,”

The trial aims to answer whether the temporary interruption of adjuvant endocrine therapy to attempt pregnancy is safe from a breast cancer relapse perspective comparatively with SOFT and TEXT trials population (that is used as external control cohort).

The long-term survival of women with HR+ breast cancer treated with standard endocrine treatment is good and the treatment benefit is independent of age at diagnosis.

After at least 18months and no more than 30 months of endocrine therapy, patients involved in the study take a three-month break in treatment before attempting pregnancy .the treatment stop then continues for up to two years to allow conception, delivery and breastfeeding (or potential failure to conceive). Endocrine therapy then restarts and continues for the duration of treatment. Women will be followed up for 10 years after study entry.

Premenopausal women with HR+ early breast cancer who received endocrine therapy for 18 to 30 months, are 42 years of age or younger at enrolment, and wish to interrupt endocrine therapy to become pregnant.

On 2 January 2020, the POSITIVE study met its target accrual, enrolling 518 patients from 203 centres from 20 countries in 4 continents. The initial target accrual was 500 patients, but due to the interest shown by young women in this study, women who already had appointments with their oncologists to enroll in the study were still able to participate.

The study is sponsored and conducted by the International Breast Cancer Study Group (IBCSG), a division of ETOP-IBCSG Partners Foundation, and by the Alliance for Clinical Trials in Oncology in North America, in collaboration with the Breast International Group (BIG). The study concept was initiated within the BIG-NCTN (National Clinical Trials Network) Endocrine Working Group and then developed and coordinated globally by the IBCSG.

Participating groups: ABCSG, BOOG, EORTC, GBECAM, GEICAM, HORG, JBCRG, NBCG, SAKK, SOLTI.

• Recruitment of patients started in 2014 and was completed in December 2019.
• 518 patients were recruited in total, from 203 participating hospitals across 20 countries
• First results have been presented  at San Antonio breast Cancer Symposium (SABCS) in December 2022
• Further follow-up is planned at least 10 years after enrolment.

203 hospitals from 20 countries around the world, from 11 BIG collaborative groups as well as independent sites.

A presentation at SABCS 2022, presented by Pr Olivia Pagani states:

At a median follow-up of 41 months, 44 participants had experienced a recurrence of breast cancer in the POSITIVE trial. The three-year rate of recurrence was 8.9 percent, which is similar to the 9.2 percent rate in the  external control cohort from SOFT/TEXT  trials.

Of 497 women , 368 (74 percent) had at least one pregnancy, and 317 (63.8 percent of all women) had at least one live birth, with a total of 365 babies born. These rates of conception and childbirth were on par with or a bit higher than rates in the general public. Trial participants were strongly recommended to resume endocrine therapy after a pregnancy attempt or success. To date, 76.3 percent have resumed their endocrine therapy.

The researchers are continuing to follow the study participants to assess recurrence risk over time. They noted that the short follow-up to date is a limitation of the POSITIVE study, as HR-positive breast cancer can recur many years after an initial diagnosis. A long follow up is planned until 10 years.

• Sun Z, Niman SM, Pagani O et al. Estimation of historical control rate for a single arm de-escalation study – Application to the POSITIVE trial. Breast 2020;53:1-7. doi: 10.1016/j.breast.2020.05.012. Epub 2020 Apr 9
• Partridge AH, Niman SM, Ruggeri M et al. Who are the women who enrolled in the POSITIVE trial: A global study to support young hormone receptor positive breast cancer survivors desiring pregnancy. Breast. 2021 Aug 3;59:327-338. doi: 10.1016/j.breast.2021.07.021.

IBCSG, Fonds Baillet-Latour, national and local funding bodies, and individual donors

NCT02308085