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 “Optimising Treatment Outcomes and Preserving Fertility in Premenopausal HR+ Breast Cancer.”

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.

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

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.”

Partridge AH, Niman SM, Ruggeri M, et al. Interrupting Endocrine Therapy to Attempt Pregnancy after Breast Cancer. N Engl J Med. 2023 May 4;388(18):1645-1656. doi: 10.1056/NEJMoa2212856.

“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.