How the PATINA Regimen Advances Maintenance Therapy for HR-Positive, HER2-Positive Metastatic Breast Cancer

In this interview with Pharmacy Times, Allison Butts, PharmD, BCOP, pharmacist manager of breast oncology and clinical pharmacy specialist at the University of Kentucky Markey Cancer Center, discusses how the PATINA regimen is changing treatment for HR-positive, HER2-positive metastatic breast cancer. Butts explains that adding the CDK4/6 inhibitor palbociclib to anti-HER2 and endocrine maintenance therapy allows clinicians to address both components of this “triple-positive” disease more effectively. She highlights patient adherence and the ability to manage overlapping treatment schedules as important considerations when selecting this strategy.

Pharmacy Times: How does the addition of palbociclib to anti-HER2 and endocrine maintenance therapy change the treatment approach for patients with HR-positive, HER2-positive metastatic breast cancer?

Allison Butts, PharmD, BCOP: This regimen—the PATINA regimen—is newer for us. Until these data came out, we really could not use CDK4/6 inhibitors in the HER2-positive space, which was a struggle for us. I think managing patients with HER2-positive and hormone receptor–positive disease poses many challenges, and being able to more optimally manage both aspects of their cancer is very important and exciting for us. Based on the data from the PATINA trial, we now have almost 4 years of disease control in these patients with what we call triple-positive breast cancer. This is a major advancement and a major new therapeutic option that we did not have before the PATINA study.

Pharmacy Times: What patient-specific factors should clinicians consider when determining who is most likely to benefit from this maintenance strategy?

Butts: One of the biggest challenges with this regimen is that there are a lot of visits involved. To be honest, we just had our first patient start this regimen last week. The anti-HER2 therapy is generally administered every 3 weeks at the infusion center, whereas palbociclib is usually administered in 4-week cycles. Therefore, it can be complicated to manage all the follow-up toxicity monitoring requirements for palbociclib, including laboratory checks at the appropriate intervals, while also incorporating the patient’s infusion appointments every 3 weeks.

One consideration is whether the patient can manage that schedule, especially at the beginning, when monitoring is more frequent. Once patients are stable and their counts have shown that they’re stable, we can space out those visits and align everything more smoothly. Patient adherence and the ability to tolerate the regimen—particularly the schedule—are important considerations that come to mind.

Pharmacy Times: What monitoring, toxicity-management, and adherence considerations should oncology pharmacists prioritize when patients receive long-term CDK4/6 inhibition alongside anti-HER2 and endocrine therapies?

Butts: As I was alluding to, laboratory monitoring is more intensive at the beginning of therapy. Specifically, with CDK4/6 inhibitors, we conduct laboratory monitoring every 2 weeks, primarily for neutropenia. Monitoring every 2 weeks for the first 2 months is required, after which we can transition to monthly monitoring of blood cell counts and potentially extend the intervals even further. The beginning of treatment is therefore the most intensive period from a CDK4/6 inhibitor monitoring standpoint.

In comparison, monitoring for anti-HER2 therapy is relatively straightforward during the maintenance phase. At this point, patients are no longer receiving cytotoxic chemotherapy, such as a taxane. They are receiving only these monoclonal antibodies, which are generally well tolerated. We monitor cardiac function every 3 months and potentially extend that interval to every 6 months. Fortunately, monitoring for anti-HER2 therapies is relatively easy during this phase of maintenance. The intensive monitoring required at the beginning of palbociclib therapy presents the greatest challenge.