This transcript has been edited for clarity.
Hi. It's Dr Kathy Miller from Indiana University, coming to you today from the 2023 ASCO annual meeting in Chicago.
It's been an exciting year for breast cancer news. I want to make sure that you hear about the two studies that I find the most impactful. One is the NATALEE study looking at ribociclib in adjuvant ER-positive patients at high risk for recurrence. You saw the press release a few weeks ago and we now have the data. There is no doubt that this is a positive trial.
The details here are important. These were pre- or postmenopausal women, and men as well. Premenopausal women and men also had an LHRH agonist in addition to an aromatase inhibitor — that could have been either letrozole or anastrozole — then randomized to ribociclib or placebo.
The dose of ribociclib that you're used to thinking about is 600 mg daily for 3 weeks and 7 days off. That's the approved dose in the metastatic setting. In the adjuvant trial, they used 400 mg, and that was intentional to try to reduce some of the toxicity because the plan was for 3 years of therapy. Managing toxicity and really making this tolerable for patients was crucial.
We've now seen the efficacy results, with a roughly 3% reduction in the risk for recurrence; 90% disease-free survival in the ribociclib arm, 87% in the control arm, some patients still having prolongation of QTc but no serious arrhythmias; some patients still with myelosuppression, but risk for serious infections was really very low.
This is going to give you a question to ponder in your high-risk, ER-positive patients who are appropriate to consider for adjuvant cyclin-dependent kinase inhibitors. Are you now on team abemaciclib or team ribociclib? We have no head-to-head trials in any setting, and I doubt that our industry colleagues are going to be interested in a head-to-head setting.
We're going to need to pay particular attention to long-term follow-up and to quality-of-life and toxicity data as to which our patients prefer. We may need to think about other ways of doing those direct comparisons with public funding, where we can get the answers our patients deserve.
I also want to think about the other end of the spectrum, those patients with HER2-positive disease. We saw fantastic results from the PHERGain study from our colleagues in Spain. This was a trial that took patients with predominantly stage II and III HER2-positive breast cancer. These are patients that we would treat with neoadjuvant chemotherapy, with dual HER2-targeted therapy.
Years ago, we saw results of some small, single-arm phase 2 studies, suggesting that some of those patients may be so sensitive to biologic therapy that they have a pathologic complete response with HER2-targeted therapy — HER2-targeted therapy with endocrine therapy if they are positive — with no chemotherapy at all. Our question has always been how to identify those patients. Can we identify them well enough that we would be comfortable not treating them with chemotherapy? Importantly, If they didn't get chemotherapy, what's their long-term outcome?
The PHERGain trial lets us look at all those things. The PHERGain trial gave patients two cycles of dual HER2-targeted therapy, pertuzumab and trastuzumab, hormone therapy if also ER positive, and they got an FDG-PET scan after two cycles of therapy.
If they had a significant PET response, those patients were then randomized to switch to chemotherapy, standard TCHP, or continue biologic therapy alone for a total of six cycles. They then went to surgery. If they had a pathologic complete response, whether they had gotten chemotherapy or no chemotherapy, they completed the HER2-targeted therapy. If they still had residual disease, they got chemotherapy if chemotherapy had not been administered before, and they may have gotten other HER2-targeted therapies if they had already received chemotherapy.
There were over 300 patients in this trial, and my memory is that roughly two thirds of them had a PET response. About 86 patients randomized to continue biologic therapy had a pathologic complete response, so about one third of those for whom the PET imaging said they were responding with biologic therapy only had a pathologic complete response.
They have now been followed for 3 years. The 3-year disease-free survival results look very reassuring. Of those 86 patients, one patient had a local recurrence and no patient had a distant recurrence.
This is what we've been waiting for. Can we identify those patients who have an excellent prognosis with biologic therapy alone so that we can avoid the toxicities? This is really where you'll see the research over the coming years in breast cancer, looking at additional therapies in high-risk patients who don't do so well with our standard therapies, and better stratification of patients who do so well with our standard therapies that we may be able to do less.
This is one of the ways that we'll be able to do that. I look forward to sharing those results with you over coming years.
I'll be back with you again soon. This is Dr Kathy Miller, from Indiana University.
Kathy D. Miller, MD, is associate director of clinical research and co-director of the breast cancer program at the Melvin and Bren Simon Cancer Center at Indiana University. Her career has combined both laboratory and clinical research in breast cancer.
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Cite this: ASCO 2023: Promising Results in Breast Cancer From NATALEE and PHERGain - Medscape - Jun 15, 2023.
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