Episode 2: The POSITIVE trial

The POSITIVE Trial, led by the Breast International Group, addressed the safety of discontinuing treatment for hormone receptor-positive breast cancer patients to attempt pregnancy. It involved around 500 patients, primarily under 42 years old, who had received 18 to 30 months of endocrine therapy and had stage 1, 2, or 3 breast cancer, mainly stage 1 and 2 (93%). Participants stopped treatment, had a four-month washout period, and could then try to conceive. Impressively, 80% of patients achieved pregnancy without significant issues in newborns’ health or birth weight.

Pregnancy success rates varied by age, with 85% for those under 35, 76% for those aged 35-40, and 52% for those aged 40-42. This suggests younger patients had better chances. Importantly, 73% of patients resumed endocrine therapy after giving birth. However, there’s room for improvement in this aspect, as endocrine therapy is crucial for treatment. Low-risk breast cancer patients on therapy for at least 18 to 30 months can consider discontinuation but should consult with their oncologists, considering factors like relapse risk, pregnancy plans, age, and existing children.

These results provide reassurance, particularly for centers already practising such recommendations. Nevertheless, the short follow-up of 42 months is a concern, given that hormone receptor-positive disease can have relapse risks extending up to seven to ten years. Longer-term data, expected over ten years, will provide a more conclusive answer for patients and clinicians.

Ref: Partridge Ann et al.,for the International Breast Cancer Study Group, and the POSITIVE Trial Collaborators; N Engl J Med 2023; 388:1645-1656