Optimizing Outcomes With CDK4/6 Inhibitors: Pharmacist-Led Education and Individualized Dose Modifications

In this interview, Rose DiMarco, PharmD, BCPS, BCOP discusses the evolving role of pharmacists in managing patients receiving CDK4/6 inhibitors for hormone receptor–positive early breast cancer. She highlights the most common treatment-related toxicities, including fatigue, nausea, hepatotoxicity, neutropenia, and diarrhea with abemaciclib, and emphasizes the importance of proactive patient education to prepare individuals for what to expect and how to manage side effects at home. DiMarco also explains how pharmacists can tailor educational tools—such as videos, printouts, or checklists—to each patient’s learning style while setting expectations for potential dose modifications to balance treatment efficacy with tolerability and long-term outcomes.

Pharmacy Times: In your opinion, which trial data have been the most practice-changing in the context of these agents for this disease setting, and why?

Rose DiMarco, PharmD, BCPS, BCOP: In my opinion, the first—or I would say the most groundbreaking—trial that I’ve seen that has been practice-changing is really the MONARCH trial leading to the approval of abemaciclib in the early breast cancer setting. It was the first CDK4/6 inhibitor approved for adjuvant treatment in patients with hormone-positive early breast cancer. This then led to the approval of ribociclib from the NATALEE trial a few years ago, which really expanded access for patients with high-risk node-negative disease who could still face a significant risk of recurrence.

Pharmacy Times: What are the most common medication-related issues you see with CDK4/6 inhibitors, and how do pharmacists intervene?

DiMarco: The most common medication-related toxicities I see with CDK4/6 inhibitors are fatigue, nausea, hepatotoxicity, neutropenia, and diarrhea—particularly with abemaciclib. As pharmacists, what we really focus on is providing high-quality patient education so that patients understand which side effects to expect, when they are likely to occur, and how to manage them at home.

Pharmacy Times: How do pharmacists educate patients on what to expect and when to report side effects that may require dose adjustments?

DiMarco: Got it. Yeah, so it’s really all about the education that patients receive. Some patients prefer videos, others like printouts, treatment calendars, or checklists—things they can take home with them. The key is understanding what the patient wants to hear and how they want to receive that information in order to provide appropriate counseling.

When it comes to dosing modifications or reductions, I tell patients upfront that we may need to reduce their dose based on side effects to find the right dose for them. What that means is we’re still aiming for strong efficacy, good data, and long-term survival, but that isn’t possible if patients can’t tolerate their therapy. So it’s about finding the right dose for the right patient. I set that expectation early so they’re not surprised if a dose reduction becomes necessary.