Fewer than 3 in 10 patients under 65 with early-stage, hormone receptor-positive breast cancer consistently filled their hormone therapy prescriptions for all five recommended years after a lumpectomy, according to an insurance claims analysis released Sept. 27 at the American Society for Radiation Oncology Annual Meeting in Boston. About 28% stayed above the standard adherence threshold through five years.
The findings, presented at the Sept. 26 to 30 meeting, have not been published in a peer-reviewed journal. They are based on pharmacy refill records, which show whether patients had medication on hand, not whether they took each dose.
The results matter for women deciding on treatment after surgery. Endocrine therapy lowers the chance that hormone-driven breast cancer returns, and for patients who skip radiation, the daily pill carries more of that protective role.
Yearly Snapshots Hid a Five-Year Drop-Off
Researchers led by Dr. Shannon Jiang, a radiation oncology resident at Washington University School of Medicine in St. Louis, analyzed Merative MarketScan commercial and multistate Medicaid claims for 17,025 patients ages 23 to 64. All had a lumpectomy and filled at least one hormone therapy prescription, and 89% also received radiation.
Patients were counted as adherent if they had medication available at least 80% of the time. In any single year, 59% to 75% met that bar. But over five years, patients steadily fell below it, leaving about 28% continuously adherent.
Patients younger than 60 had a 20% to 25% higher risk of becoming nonadherent across the thresholds studied, according to a summary of the study findings.
"Our findings are a reminder that doctors prescribing endocrine therapy for five years and patients actually taking the medication for five years are not the same thing," Jiang said.
Endocrine therapy works by blocking or lowering the hormones that can fuel hormone receptor-positive tumors, which make up about 80% of breast cancers. Tamoxifen and aromatase inhibitors such as anastrozole, letrozole, and exemestane are taken as daily pills, usually for at least five years. Gaps in treatment can leave patients without that protection for weeks or months at a time.
Skipping Radiation Puts More Weight on a Daily Pill
For some older patients with lower-risk tumors, clinical trials have shown radiation can be skipped without lowering overall survival, though the cancer is more likely to return in the treated breast. In the PRIME II trial of women 65 and older, 10-year local recurrence was 9.5% without radiation and 0.9% with it, while overall survival was nearly identical. Patients in that trial were expected to take hormone therapy.
In the new analysis, patients who did not receive radiation were twice as likely to fall below a 50% medication-possession level and significantly more likely to fall below the 60% and 70% levels. The difference was not statistically significant at the standard 80% threshold.
The study was not designed to explain why. Patients receiving radiation may have had more frequent contact with their cancer care teams, or the groups may have differed in access to care or treatment preferences.
The question is becoming more pressing as studies test skipping radiation in younger women. "As studies expand radiation therapy omission to younger patients with favorable tumors, it becomes increasingly important to understand what happens with long-term adherence to endocrine therapy in real-world settings," Jiang said. She is scheduled to discuss the findings at an ASTRO news briefing on Tuesday, Sept. 29.
Dr. Jose G. Bazan, chair of ASTRO's Breast Cancer Resource Panel and a radiation oncologist at City of Hope in Duarte, California, said the study shows how difficult long-term adherence can be. "The goal is to choose a treatment plan that patients can realistically maintain over time," he said.
Limits of a Pharmacy Claims Analysis
This was an observational study presented as a meeting abstract. It found an association between skipping radiation and lower adherence, not proof that radiation causes people to keep taking their pills.
The database did not include anyone older than 64, the age group that currently makes up much of the population considered for skipping radiation. Jiang's team plans to add Medicare data. Refill records also cannot capture doses skipped at home.
The pattern fits earlier research. A 2014 review in Cancer Prevention Research estimated that only about half of women complete five years of adjuvant hormone therapy in routine practice and linked nonadherence to factors including medication costs, younger or older age, and poor patient-doctor communication. A systematic review of adherence interventions described nonadherence as a significant problem, especially in minority populations.
Side Effects, Refills, and Questions for the Care Team
Common side effects include hot flashes and vaginal discharge with tamoxifen, and joint and muscle pain, hot flashes, vaginal dryness, and bone thinning with aromatase inhibitors. Joint stiffness can be severe enough that some patients stop treatment.
Patients should not stop or pause hormone therapy on their own. Telling an oncologist about side effects early can open options, such as treating specific symptoms or switching to a different medication. Refill reminders, pharmacy auto-refill, and 90-day supplies may help prevent gaps, and patients facing high copays can ask about generics or financial assistance programs.
People weighing whether to skip radiation can ask their care team how realistic five years of daily medication is for them and how their risk of the cancer returning would change with and without radiation. Caregivers can help by tracking refills.
A peer-reviewed publication and the planned Medicare analysis are the next steps to watch.
Key Questions Answered
What did the study find? About 28% of patients under 65 stayed consistently on hormone therapy through five years after lumpectomy, based on insurance refill records.
Who was studied? 17,025 patients aged 23 to 64 with early-stage, hormone receptor-positive breast cancer covered by commercial insurance or Medicaid.
Did skipping radiation lower adherence? Patients who skipped radiation were more likely to have large gaps in medication, but the study does not show that radiation caused better adherence.
Is the study peer reviewed? Not yet. It was released Sept. 27 at the ASTRO Annual Meeting in Boston.
Why do patients stop hormone therapy? Side effects such as hot flashes and joint pain, along with cost, age, and communication with doctors, are among the factors linked to stopping.
Should I stop my medication if side effects are hard? No. Talk with your oncologist first. Side effects can often be managed, or the medication can be changed.
Published by Medicaldaily.com
