Breast Cancer Patients Struggle with Long-Term Therapy
Most patients with ER-positive breast cancer stop taking prescribed endocrine therapy within five years of their lumpectomy.
Updated on Oct. 16, 2026 in Cancer
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A new study tracking 17,025 women with ER-positive breast cancer found that fewer than 30 percent remain adherent to prescribed endocrine therapy five years after lumpectomy. The findings suggest significant challenges in long-term treatment maintenance for patients managing this type of cancer.
Why it matters
Endocrine therapy is a cornerstone of preventing recurrence in ER-positive breast cancer, making long-term adherence critical for effective health outcomes. Understanding why adherence drops over time is essential for patients and clinicians to improve support systems for those on these long-term regimens.
This retrospective analysis of 17,025 women with ER-positive early-stage breast cancer found that adherence drops significantly after the first year. While 34.6 percent of patients were adherent in year one, fewer than 30 percent remained on track by year five.
The players
Washington University School of Medicine
An academic medical institution that led the research analysis on breast cancer treatment adherence.
ASTRO
The American Society for Radiation Oncology, a professional organization that hosts an annual meeting for the oncology community.
The details
Researchers utilized medication possession ratios, which track how often a prescription is refilled, to evaluate adherence across the study population. The data indicate that while 77 percent of patients who stayed on therapy maintained consistent use in years two through five, the overall cohort saw a sharp decline in treatment continuity. The analysis also noted that younger patients were less likely to discontinue therapy, while receipt of adjuvant radiation was linked to higher adherence in older cohorts.
Timeline
September 26 to 30, 2026: The study was presented at the ASTRO annual meeting in Boston.
Year 1: 34.6 percent of patients remained adherent to their medication.
Years 2 to 5: 77 percent of patients remaining on therapy met the 80 percent adherence threshold.
Year 5: Fewer than 30 percent of patients continued to follow their prescribed endocrine therapy.
Health Landscape
This research follows a growing body of work presented at the ASTRO annual meeting focused on optimizing the long-term cancer care continuum. It highlights a common gap between clinical treatment guidelines and real-world patient outcomes in survivorship care.
If you are prescribed endocrine therapy for ER-positive breast cancer, it is worth discussing potential barriers to adherence with your oncology team. Maintaining consistent communication about side effects or logistical challenges can help ensure your treatment plan remains sustainable.
The takeaway
Long-term adherence to endocrine therapy remains a significant challenge, with a clear decline in consistency after the first year of treatment. Patients should maintain open conversations with their physician about any difficulties in fulfilling prescriptions to ensure continued protection against recurrence.
Further reading
Learn more about navigating Cancer treatment plans and survivorship care.
Source note: This article includes information reported by Oncology Nurse Advisor.
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