Emerging Biomarkers and Precision Treatment Sequencing in Breast Cancer Care

In this interview with Pharmacy Times at Oncology Pharmacists Connect in Austin, TX, Allison Butts, PharmD, BCOP, Pharmacist Manager, Oncology, Breast Oncology, and Clinical Pharmacy Specialist, UK Markey Cancer Center, discusses the expanding role of biomarkers in guiding treatment decisions for patients with breast cancer. She highlights the increasing complexity of identifying and sequencing targeted therapies based on actionable alterations such as ESR1, PIK3CA, and PTEN mutations, while ensuring appropriate genomic testing is performed. Butts also reviews challenges associated with integrating emerging therapies into practice, including regulatory timelines, appropriate utilization following approval, and the need to align treatment selection with available evidence.

Pharmacy Times: What biomarkers, genomic tests, or patient-specific factors do you believe are having the greatest impact on treatment decision-making today, and how should oncology pharmacists stay current with these developments?

Allison Butts, PharmD, BCOP: There is a growing number of biomarkers available today, whether that involves genomic testing, genetic testing, or any number of other diagnostic tools that we can use. Because of that, it is difficult to make broad statements that apply to all breast cancer. When I think about subsets of breast cancer where this is particularly relevant, hormone receptor-positive disease is the first that comes to mind.

One of the challenges we are facing is the increasing number of targeted therapies available. We are now looking at ESR1 mutations, PIK3CA mutations, PTEN alterations, and many other biomarkers that clinicians need to be aware of. This creates additional complexity because different treatments align with each of these molecular alterations. As a result, we must determine not only which therapies are appropriate for a given patient, but also which should be used first and which should be reserved for later lines of therapy.

Ultimately, a major challenge is determining how to optimally sequence these available treatments while also ensuring that the appropriate biomarker testing is performed at the right time.

Pharmacy Times: Many promising advances emerge from clinical trials, but implementation in real-world practice can be challenging. What are some of the biggest barriers to translating new breast cancer discoveries into routine patient care, and how can pharmacists help bridge that gap?

Butts: One of the most obvious barriers is that many of these drugs are not approved immediately. For example, giredestrant, which we discussed during this presentation, is not yet FDA-approved. The data are very encouraging, and there is a great deal of excitement surrounding the agent, but we still have to wait until its Prescription Drug User Fee Act (PDUFA) date later this year. Even after a positive regulatory decision, there will likely be additional time before the drug is widely available for clinical use. That is the first challenge.

Another challenge is that once new drugs are approved, there can be a tendency to use them in multiple clinical scenarios that may not have been studied. It is important to understand the specific approvals, the patient populations in which the therapies were evaluated, and where their use is most appropriate. Pharmacists play an important role in helping to guide appropriate utilization of new therapies and ensuring that treatment decisions remain aligned with the available evidence.

Pharmacy Times: As treatment options become increasingly individualized, how has the role of the oncology pharmacist changed within the multidisciplinary breast cancer care team, particularly regarding treatment selection, patient education, and adherence support?

Butts: One treatment class that immediately comes to mind is PI3K inhibitors. These agents are known to cause significant hyperglycemia and highlight many of the considerations you mentioned related to treatment selection, patient counseling, and ongoing monitoring.

From a treatment selection standpoint, it is important to determine whether a patient has preexisting diabetes and, if so, whether it is well controlled. It is also essential to have a strong working relationship with the endocrinologist or other clinician managing the patient's diabetes. Patient counseling is equally important because these therapies often require substantial monitoring and management. Patients may need to come into the clinic frequently for fasting glucose assessments, or they may be asked to perform glucose monitoring at home and report those results back to the care team.

Once those results are available, the next step is determining how to manage them. Do dose adjustments need to be made? Should therapy be held? Is there a need to escalate antihyperglycemic treatment? These are all important considerations. PI3K inhibitors are a particularly complex drug class and require significant pharmacist involvement to ensure that each of these steps is appropriately managed, that patients are monitored as recommended, and that the necessary follow-up occurs behind the scenes to support safe and effective treatment.

Pharmacy Times: Looking ahead, what emerging trends in personalized breast cancer care are you most excited about, and what impact do you anticipate they will have on patient outcomes over the next few years?

Butts: One area where I think oncology care will become increasingly personalized is the growing number of therapies being developed for the same indication or biomarker. As more treatment options become available, pharmacists will play an important role in understanding the nuances between these agents.

Those differences may relate to toxicity profiles, making one drug a better fit for a particular patient based on their comorbidities. Other considerations may involve monitoring requirements, treatment adherence, and a patient's ability to comply with a given treatment plan. Pharmacists are uniquely positioned to assess where a patient is in their treatment journey, determine what is feasible for them, and identify potential barriers to care.

In addition, pharmacists can help guide providers by evaluating efficacy data alongside these practical considerations. Ultimately, their role is to help ensure that the therapy selected is not only effective but also the most appropriate option for the individual patient in front of us.