Study Identifies Factors Impacting Adherence to Oral Medications for Metastatic Breast Cancer

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A recent study published by Conley et al in Breast Cancer Research and Treatment aimed to evaluate factors that influence the ability of people with metastatic breast cancer to adhere to their prescribed regimen of oral anticancer medication. Researchers found that multiple factors affected adherence, including side effects, cost of the therapy, patients' knowledge about the medication, and communication with their care team.

In the United States, about 10% of breast cancers are diagnosed at the metastatic stage, and 20% to 30% of early-stage breast cancers progress to metastasis. Patients are responsible for remembering and maintaining their oral anticancer medication schedule. Prior research has investigated adherence to oral anticancer drugs among patients with early-stage breast cancer, but until now, no studies had been performed in people with metastatic disease. 

CDK4/6 inhibitors like palbociclib, ribociclib, and abemaciclib are oral cancer therapies specifically for metastatic breast cancer. Although not a cure, these medications have been shown to slow metastatic breast cancer progression and extend survival. Patients typically take them for as long as they remain effective. While convenient, these medications may have a high out-of-pocket cost and, in some patients, cause side effects such as diarrhea, fatigue, and/or nausea.

"This study shows that patients' ability to take their CDK4/6 inhibitors as prescribed can be influenced by their understanding of the medication and its use, the side effects they experience, support from the care team, and financial factors," explained Deena M. Atieh Graham, MD, a medical oncologist at Hackensack University Medical Center who coauthored the study. "Assessing these factors when a patient begins CDK4/6 inhibitor treatment and periodically thereafter can help us identify these issues earlier and address them sooner. Enhancing adherence to treatment could reduce health-care costs and improve metastatic breast cancer outcomes."

Survey Results

The study surveyed 25 patients with metastatic breast cancer, 9 of their caregivers, and 13 cancer care providers at two National Cancer Institute–designed Comprehensive Cancer Centers: Georgetown Lombardi Comprehensive Cancer Center and H. Lee Moffitt Cancer Center & Research Institute.

Of note, the investigators found that:

  • Adherence is high when patients understand how the treatment works and believe it is effective; adherence decreases with poor patient understanding.
  • Side effects could cause interruptions in taking the medication or reducing the dose, though patients generally felt CDK4/6 inhibitor–associated side effects were not as bad as those experienced with chemotherapy and were acceptable given the drug's effectiveness.
  • Effective communication with the care team improved adherence to therapy, especially the assistance of nurses, pharmacists, and social workers.
  • Cost may be a barrier to adherence, with medication refills sometimes being delayed while waiting for insurance approval and financial assistance criteria creating a coverage gap for some patients in need.
  • Family and friends often provided motivation for patients to take their medicine.

The researchers concluded that future studies should include larger groups of patients with metastatic breast cancer to inform the design of effective interventions to improve oral medication adherence.

Disclosure: For full disclosures of the study authors, visit

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.