Adherence to Aromatase Inhibitors ± Abemaciclib Treatment in Patients With Early-stage HER2-negative Breast Cancer (ONCO-Adher)

March 4, 2026 updated by: Institute of Oncology Ljubljana

ONCO-ADHER: Adherence to Treatment With Aromatase Inhibitors With or Without Abemaciclib in Patients With Early-stage, Endocrine-dependent, HER2-negative Breast Cancer

Around 90% of breast cancer patients are diagnosed at an early stage and approximately 70% are hormone receptor-positive and HER2-negative (HR+/HER2-). Despite advancements in adjuvant endocrine therapy, 20-30% of early-stage breast cancer patients relapse within the first decade post-surgery. A recent clinically meaningful therapeutic option for these patients has been cyclin-dependent kinases 4/6 inhibitors (CDK4/6 inhibitors). Abemaciclib and ribociclib were assessed in the adjuvant setting, both showing improvement in invasive disease-free survival (IDFS). Abemaciclib has been approved by the FDA and EMA for HR+/HER2- early breast cancer at high risk of disease recurrence and is the first addition to the Slovenian treatment regimen in routine clinical practice.

Poor medication adherence can directly affect the effectiveness of treatment for early HR+/HER2- breast cancer. While adherence data in patients treated with aromatase inhibitors are available, the adherence rate in patients with early HR+/HER2- breast cancer taking abemaciclib remains unclear.

In this study, investigators hypothesize that patients receiving abemaciclib in combination with aromatase inhibitors will have lower medication adherence and higher discontinuation rates compared to those receiving aromatase inhibitors alone. It is expected that patients with better quality of life, better cognitive functioning, and a more positive attitude toward their therapy will demonstrate higher medication adherence rates. Adherence may also be influenced by additional factors, such as age and prior treatments.

Study Overview

Status

Recruiting

Conditions

Detailed Description

Poor medication adherence can directly affect the effectiveness of treatment for early HR+/HER2- breast cancer. While data on medication adherence in patients taking aromatase inhibitors are available, the adherence rate in patients with early HR+/HER2- breast cancer taking abemaciclib remains unclear. Due to the differing characteristics of these treatment modalities, particularly their distinct safety profiles, medication adherence and persistence may vary between them.

It is hypothesized that patients receiving abemaciclib in combination with aromatase inhibitors will have lower medication adherence and higher discontinuation rates compared to those receiving aromatase inhibitors alone. It is also expected that patients with better quality of life, better cognitive functioning, and a more positive attitude toward their therapy will demonstrate higher medication adherence rates. Additionally, factors such as age and prior treatments may contribute to adherence outcomes.

Study Type

Observational

Enrollment (Estimated)

319

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

  • Name: Cvetka Grašič Kuhar, PhD
  • Phone Number: 00386 1 5879 090
  • Email: cgrasic@onko-i.si

Study Locations

  • Slovenia
      • Ljubljana, Slovenia, 1000
        • Recruiting
        • Institute of Oncology Ljubljana
        • Contact:
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Eligible adult women with early HR+ HER2- breast cancer patients.

Description

Inclusion Criteria:

  • Female,
  • Early HR+/HER-2- BC,
  • Patient is receiving adjuvant therapy with an aromatase inhibitor (letrozole, anastrozole or exemestane), with or without a CDK4/6 inhibitor abemaciclib, for no more than 18 months,
  • Treatment of BC is being conducted at OIL,
  • Patient has mandatory health insurance through Health Insurance Institute of Slovenia,
  • Patient understands Slovenian language, and
  • Patient agrees to participate in the study and provides written informed consent.

Exclusion Criteria:

  • Metastatic HR+/HER2-negative breast cancer
  • Previous treatment for breast cancer with an aromatase inhibitor, with or without a CDK4/6 inhibitor, for early breast cancer prior to the current adjuvant treatment line

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Aromatase inhibitor + abemaciclib
Adult women with early HR+ HER2- breast cancer, eligible for treatment with aromatase inhibitor + abemaciclib, both prescribed prior inclusion into study, irrespective of protocol, as per regular clinical practice
Aromatase inhibitor
Adult women with early HR+ HER2- breast cancer, eligible for treatment with aromatase inhibitor, prescribed prior inclusion into study, irrespective of protocol, as per regular clinical practice

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Medication adherence (Proportion of Days Covered, PDC) at Month 3
Time Frame: Month 3 after treatment initiation
Medication adherence measured as Proportion of Days Covered (PDC), calculated from pill count data and expressed as percentage (%). Participants with PDC ≥80% will be classified as adherent. Self-reported adherence will additionally be assessed using the Medication Adherence Report Scale (MARS-5; score range 5-25, higher scores indicate better adherence).
Month 3 after treatment initiation
Medication adherence (Proportion of Days Covered, PDC) at Month 6
Time Frame: Month 6 after treatment initiation
Medication adherence measured as Proportion of Days Covered (PDC), calculated from pill count data and expressed as percentage (%). Participants with PDC ≥80% will be classified as adherent. Self-reported adherence will additionally be assessed using the Medication Adherence Report Scale (MARS-5; score range 5-25, higher scores indicate better adherence).
Month 6 after treatment initiation

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
EORTC QLQ-C30 score at Baseline
Time Frame: Baseline visit
Quality of life assessed using the EORTC QLQ-C30 questionnaire. Scores are transformed to a 0-100 scale (higher scores on functional and global scales indicate better functioning; higher scores on symptom scales indicate greater symptom burden).
Baseline visit
EORTC QLQ-C30 score at Month 3
Time Frame: Month 3
Quality of life assessed using the EORTC QLQ-C30 questionnaire. Scores are transformed to a 0-100 scale (higher scores on functional and global scales indicate better functioning; higher scores on symptom scales indicate greater symptom burden).
Month 3
EORTC QLQ-C30 score at Month 6
Time Frame: Month 6
Quality of life assessed using the EORTC QLQ-C30 questionnaire. Scores are transformed to a 0-100 scale (higher scores on functional and global scales indicate better functioning; higher scores on symptom scales indicate greater symptom burden).
Month 6
EORTC QLQ-BR23 score at Baseline
Time Frame: Baseline visit
Quality of life assessed using the EORTC QLQ-BR23 questionnaire. Scores are transformed to a 0-100 scale (higher scores on functional scales indicate better functioning; higher scores on symptom scales indicate greater symptom burden).
Baseline visit
EORTC QLQ-BR23 score at Month 3
Time Frame: Month 3
Quality of life assessed using the EORTC QLQ-BR23 questionnaire. Scores are transformed to a 0-100 scale (higher scores on functional scales indicate better functioning; higher scores on symptom scales indicate greater symptom burden).
Month 3
EORTC QLQ-BR23 score at Month 6
Time Frame: Month 6
Quality of life assessed using the EORTC QLQ-BR23 questionnaire. Scores are transformed to a 0-100 scale (higher scores on functional scales indicate better functioning; higher scores on symptom scales indicate greater symptom burden).
Month 6
Beliefs about Medicines Questionnaire (BMQ) score at Baseline
Time Frame: Baseline visit
Beliefs about medicines assessed using the Beliefs about Medicines Questionnaire (BMQ). Items are rated on a 5-point Likert scale and summed to generate questionnaire scores.
Baseline visit
Beliefs about Medicines Questionnaire (BMQ) score at Month 3
Time Frame: Month 3
Beliefs about medicines assessed using the Beliefs about Medicines Questionnaire (BMQ). Items are rated on a 5-point Likert scale and summed to generate questionnaire scores.
Month 3
Beliefs about Medicines Questionnaire (BMQ) score at Month 6
Time Frame: Month 6
Beliefs about medicines assessed using the Beliefs about Medicines Questionnaire (BMQ). Items are rated on a 5-point Likert scale and summed to generate questionnaire scores.
Month 6
FACT-Cog score at Baseline
Time Frame: Baseline visit
Cognitive functioning assessed using the Functional Assessment of Cancer Therapy-Cognitive Function (FACT-Cog) questionnaire. Items are rated on a 0-4 scale and summed to generate domain and total scores (higher scores indicate better perceived cognitive functioning).
Baseline visit
FACT-Cog score at Month 3
Time Frame: Month 3
Cognitive functioning assessed using the Functional Assessment of Cancer Therapy-Cognitive Function (FACT-Cog) questionnaire. Items are rated on a 0-4 scale and summed to generate domain and total scores (higher scores indicate better perceived cognitive functioning).
Month 3
FACT-Cog score at Month 6
Time Frame: Month 6
Cognitive functioning assessed using the Functional Assessment of Cancer Therapy-Cognitive Function (FACT-Cog) questionnaire. Items are rated on a 0-4 scale and summed to generate domain and total scores (higher scores indicate better perceived cognitive functioning).
Month 6
Adverse events during follow-up
Time Frame: From treatment initiation through Month 6
Number of participants experiencing at least one adverse event and total number of adverse events recorded during follow-up. Adverse events will be summarized by severity and seriousness.
From treatment initiation through Month 6

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Institute of Oncology Ljubljana

Collaborators

University of Ljubljana

Investigators

  • Principal Investigator: Erika Matos, PhD, Institute of Oncology Ljubljana, Slovenia

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

January 5, 2025

Primary Completion (Estimated)

March 1, 2027

Study Completion (Estimated)

March 1, 2027

Study Registration Dates

First Submitted

October 16, 2024

First Submitted That Met QC Criteria

October 18, 2024

First Posted (Actual)

October 21, 2024

Study Record Updates

Last Update Posted (Actual)

March 6, 2026

Last Update Submitted That Met QC Criteria

March 4, 2026

Last Verified

March 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • ORI2024-001

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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