Comparison of IV vs SQ Dosing and Patient Factors
Jacob Kettle, PharmD, BCOP, and Allison Butts, PharmD, BCOP, discuss the loading dose for IV vs SQ and the reduced chair-time with SQ. They also talk about the improved quality of life for patients without a porta-a-cath.
Jacob Kettle, PharmD, BCOP: When we talk about this new dosage form, it’s a huge departure from what we’re used to doing. How is this product is dosed, and what is your experience with the subcutaneous delivery? How do you connect the dots from something we’re used to doing 1 way and now doing it an entirely different way?
Allison Butts, PharmD, BCOP: One of the points is that trastuzumab and pertuzumab in their standard IV [intravenous] form require loading doses at a higher dose as well as a longer infusion time. For some of these patients, you’re initially looking at 2½ hours just of monoclonal antibody infusion time for dose No. 1. After that, both get cut down to 30 minutes each, so you’re at 2½ hours to 1 hour. It’s obviously a significant time requirement for the patient to be here.
I keep going back to the chair time and the opportunity cost: That’s time that another patient is not able to be scheduled for their therapy. If you have a therapy that can be given over a couple of minutes rather than 2½ hours, then that’s a huge benefit for sure. This particular drug combination has a loading dose still. The dose of the pertuzumab is higher with cycle 1 than it is with subsequent cycles, but the infusion time means about the same, so that doesn’t necessarily impact the patient.
It’s a consideration in terms of operationalizing it and making sure you have the correct products and the correct dosing being given to the patient. Conversely, the subcutaneous trastuzumab by itself does not have a loading dose, and for the combination product, the trastuzumab dose is constant throughout. That’s another hurdle that sometimes comes up with patient care: What do you do when a patient gets off-track with their trastuzumab doses?
They’re delayed because of a drop in cardiac function, they’re noncompliant, and they’ve got other toxicities that therapy is on hold for. Do you reload that patient or not? Some of these therapies that get rid of that loading question are helpful from a clinical perspective because you don’t have to be as concerned about the time between doses and if you need to up your dose or not.
Jacob Kettle, PharmD, BCOP: It’s important. We come across this with nurses and our providers: How in the world can we get away with this now? A lot of this comes from our understanding over the last 20 years. When we started with monoclonal antibodies, we dosed them all as if they were the same as chemotherapy. We’ve learned through that time that these are radically different. This is not a product that goes in and out of the body quickly; you have to recover from it. It’s about sustained exposure.
That’s where you can absolutely get away with a flat dose, and you can monitor a pharmacokinetic analysis that looks only at what the trough levels are. If the trough level is high enough, we know that, throughout the entire treatment period, they’ve been in that healthy therapeutic range, and there doesn’t seem to be these large molecules. They stay predominantly in the vascular space, so we all have roughly the same intravascular volume, at least as adults.
It makes pretty good sense that we can do it this way. In terms of sustained exposure, a subcutaneous injection actually makes more sense to achieve that. All those things help us bridge that gap, at least in my terms. It’s definitely a major change in the way of thinking. I wanted to piggyback again off something you said: What does this do to chair time?
We [at the University of Missouri Health Care] are seeing more and more patients year over year, and I’m sure that’s the same story throughout just about every institution in the country. We have an aging demographic in the United States, and that’s where the bulk of cancer occurs: later in life. We are wrestling with the challenge of where we put all these people. The way I think about it is this: How do we expand our footprint without changing geographically for space? It’s difficult.
On a university campus, you’re in the same boat. Where do we grow and expand to when we’re already locked in all around? It’s expensive to build new facilities, so these kinds of tools can be extremely helpful not just in delivering on quality experience for a patient but allowing us to maintain and grow our mission of serving as many people in our community as we can.
Allison Butts, PharmD, BCOP: Another factor, which is the last factor I’ll mention in terms of patient satisfaction and the patient experience, is that patients no longer require port-a-catheter at this point for these therapies. For a lot of patients, they don’t notice the port. It becomes part of them, and it’s fine. A lot of other patients see that as something that’s uncomfortable for them, and it’s also a constant reminder that they have cancer. If we could take out the port-a-catheter from the equation and make patients more comfortable and make them feel more “normal” in how they feel and how their bodies are feeling to them, that’s another major benefit to these therapies.