Panelists discuss: Why do HR+ BC patients pause or discontinue endocrine therapy?

By Lisa Marie Basile | Fact-checked by MDLinx staff

Published March 7, 2025

Key Takeaways

Conference Buzz

“The rate of discontinuation of adjuvant hormonal therapy with HR+ is very, very high. [...] I always tell [patients] my favorite therapy for them is the one they're going to take.” — Kelly E. McCann, MD, PhD, of UCLA Health

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This article is part of our Miami Breast Cancer Conference 2025 coverage. Explore more.

Poor adherence to endocrine therapy is an ongoing challenge in HR+ breast cancer treatment. Despite its proven benefits, many patients discontinue adjuvant therapy, a trend that concerns oncologists like Kelly E. McCann, MD, PhD, of UCLA Health. “The rate of discontinuation of adjuvant hormonal therapy with HR+ is very, very high,” she says.

This was a hot topic of discussion in the session “Optimizing Treatment Outcomes and Preserving Fertility in Premenopausal HR+ Breast Cancer.”

From debilitating side effects to financial burdens and even a lack of trust in the treatment itself, the reasons for stopping therapy are complex. But for physicians, the key question remains: How can they improve adherence and ensure patients receive the full benefit of their prescribed treatment?

Experts speculate why

There are plenty of reasons, Dr. McCann says, including things like adverse effects and cost, poor patient-provider relationship, and depression. Another big one? “A lack of belief in the therapy,” she says. “I spend a good hour with [each patient] about where to put their diagnosis in the scaffold of information coming in. If they don’t believe in your treatment, they’re not going to take your treatment.”

"I always tell [patients] my favorite therapy for them is the one they're going to take."

— Kelly E. McCann, MD, PhD

Dr. McCann says it’s important to improve patient education and counseling. “Ideally, we have enough time to counsel our patients,” she says. She also tries to address the side effects by referring patients to other providers for care (like for weight loss or gynecological issues), validating their feelings, and promoting healthy lifestyle behaviors like exercising and eating healthy.

Pausing therapy to start a family

The panel also discussed what they’d do if a patient wanted to pause their endocrine therapy to try and conceive—a hotly debated topic.

They pointed to data from the POSITIVE Trial, which found that “among select women with previous hormone receptor-positive early breast cancer, temporary interruption of endocrine therapy to attempt pregnancy did not confer a greater short-term risk of breast cancer events, including distant recurrence, than that in the external control cohort. Further follow-up is critical to inform longer-term safety.”^[]

“Resuming endocrine therapy post-delivery is essential,” says Rebecca Shatsky, MD, medical oncologist and Associate Professor of Medicine at UC San Diego Health. “When you have a new baby, you are feeling a loss of control, so the idea of restarting endocrine therapy, which didn’t make you feel great to begin with, is extremely overwhelming. So we need to state these outcomes definitively. It’s essential to their care,” Dr. Shatsky says.