Addressing Unmet Needs in Personalized Breast Cancer Treatment and ADC Sequencing

In this interview with Pharmacy Times, Megan May, PharmD, BCOP, FHOPA, FAPO, ambulatory oncology clinical pharmacy specialist at Baptist Health Systems, discusses persistent unmet needs in breast cancer treatment despite recent therapeutic advances. May highlights unanswered questions about sequencing antibody-drug conjugates (ADCs), switching payloads, and selecting therapies for patients with multiple actionable mutations. She explains how oncology pharmacists can support personalized treatment by ensuring appropriate tissue or circulating tumor DNA testing is performed as the disease progresses. May also emphasizes the importance of reviewing prescription medications, over-the-counter products, and supplements to prevent interactions that could compromise treatment safety or efficacy.

Pharmacy Times: What unmet needs still exist in breast cancer treatment despite the number of recent therapeutic advances?

Megan May, PharmD, BCOP, FHOPA, FAPO: One unmet need that we’re still looking at in breast cancer is the sequencing of antibody-drug conjugates (ADCs). We know they have good efficacy in breast cancer, but which one should we give first? Is one still effective after you use one ADC? We talk about switching payloads between the different agents, but do you give chemotherapy in between or not? There are still a lot of unanswered questions about the appropriate sequencing of ADCs.

Another unmet need is determining what to do when patients harbor more than one mutation. For example, in early-stage, hormone receptor–positive, HER2-negative breast cancer, what if a patient has both an ESR1 mutation and a PIK3CA mutation? Which one do you target first? I think we still need more data on how to sequence all of these agents so that we can provide the most robust efficacy for patients and know which medication to use in the next line of therapy.

Pharmacy Times: How are oncology pharmacists helping patients navigate increasingly personalized breast cancer treatment plans?

May: In breast cancer, we’re now seeing that treatment is highly personalized. One role pharmacists can play is ensuring that we conduct appropriate testing in these patients. For example, in the metastatic hormone receptor–positive, HER2-negative breast cancer setting, we should ensure that, at the first progression, we send tissue for testing or conduct circulating tumor DNA (ctDNA) testing to determine whether any biomarker mutations were acquired during that progression. Pharmacists can help ensure that we use the most appropriate agent and conduct all appropriate molecular testing so that we can match the right drug with the right mutation to best serve our patients.

Pharmacy Times: What are some of the most common questions or concerns patients have when starting newer breast cancer therapies, and how can oncology pharmacists help address them?

May: I’ve noticed that more patients are asking me about supplements and herbal medications. As an oncology pharmacist, when I meet with patients, I make sure to identify all the medications they’re taking—not only prescription medications but also those they’re obtaining over the counter. I explain the importance of letting us know everything they’re taking so that I can ensure there are no interactions with the medications we prescribe.

I also think it’s important to tell patients upfront, ‘If you start any new medication, whether it’s an over-the-counter medication or a new prescription, just give me a quick call.’ I give them my phone number and explain that I can look it up in a few minutes and tell them whether it’s safe to take. I want to ensure that what we’re doing for our patients is safe and that the other medications they’re taking don’t interfere with the best treatment for their breast cancer.