Low Endocrine Therapy Adherence for Breast Cancer Post-Pregnancy

TOPLINE:

Among breast cancer survivors who became pregnant, 34% resumed endocrine therapy (ET) by 2 years postdelivery, with a 19% cumulative incidence of subsequent breast cancer events at 10 years.

METHODOLOGY:

• The POSITIVE trial previously reported that women who interrupted ET for pregnancy, 73% resumed treatment with a low disease recurrence rate of 9%.
• The authors of the new research aimed to investigate whether ET resumption and breast cancer recurrence rates are as favorable in routine oncology practice outside of clinical trials. This study integrated data from both community and academic health systems to provide a view of real-world outcomes.
• The researchers analyzed 215 women diagnosed with stages 0-III breast cancer between January 2000 and October 2024 who later became pregnant, with a median follow-up of 9.7 years.
• Analysis integrated medical records from health systems with demographic and survival data from the California Cancer Registry, evaluating ET use, breast imaging, pregnancy outcomes, and subsequent breast cancer events.
• Participants had a median age of 33.6 years at diagnosis, with 76% having hormone receptor–positive breast cancer, and 28% utilized assisted reproductive technologies.

TAKEAWAY:

• After the landmark SOFT/TEXT trials publication in 2014-2015, the median ET duration increased from 4.1 to 4.7 years (P = .02), and ovarian suppression use rose from 8% to 45% (P
• Among women who paused ET for pregnancy, 48% resumed treatment by 10 years postdelivery, with those who resumed more likely to have invasive disease (97% vs 48%; P
• The 10-year cumulative incidence of subsequent breast cancer events was 19%, with no significant difference by stage (22%, 18%, 20%, and 16% for stages 0, I, II, and III, respectively; P = .53).
• Women who resumed ET were more likely to have received chemotherapy (83% vs 61%; P = .03) and radiotherapy (59% vs 32%; P = .01) than those who did not resume ET.
• The median ET pause duration for pregnancy was 21.0 months, while the overall median ET duration was 4.5 years.

IN PRACTICE:

“These findings raise concern that post-pregnancy ET resumption is lacking in oncology practices, which may contribute to suboptimal breast cancer outcomes…competing priorities of early parenthood and a limited understanding of ET’s importance may play a role,” wrote the authors of the study.

SOURCE:

The study was led by Julia D. Ransohoff, MD, of Stanford University School of Medicine in Stanford. It was published online on February 13 in JAMA Oncology.

LIMITATIONS:

According to the authors, limitations included the secondary research use of clinical data and potential missing information from outside the two studied healthcare systems, although linkage to statewide California Cancer Registry records helped reduce such gaps. The small sample size was noted as another limitation, reflecting the relative rarity of the target population.

DISCLOSURES:

This study received support from multiple organizations including the Breast Cancer Research Foundation, Susan and Richard Levy Gift Fund, Suzanne Pride Bryan Fund for Breast Cancer Research, Jan Weimer Junior Faculty Chair in Breast Oncology, Regents of the University of California’s California Breast Cancer Research Program, BRCA Foundation, G. Willard Miller Foundation, Carole and Alan Kushnir Charitable Fund, Nancy McDaniel PlayForHer Fund, and Biostatistics Shared Resource of the NIH-funded Stanford Cancer Institute.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.