The secondary primary endpoint results from the PHERgain study, presented at the annual meeting of the American Society of Clinical Oncology, provide more evidence to support a strategy that avoids chemotherapy as long as patients show signs of response to hormone therapy via PET scans. The results revealed that 98.8% (95% confidence interval, 96.3-100.0) of 86 patients who received treatment with trastuzumab and pertuzumab – but no chemotherapy – remained cancer free and alive 3 years after surgery (invasive disease–free survival).
“Only 1 out of 86 patients experience disease recurrence ... in those patients who never received chemotherapy,” said study lead author Javier Cortés, MD, PhD, an oncologist with Ramón y Cajal University Hospital, Madrid, during his presentation at the meeting.
As Dr. Cortés noted, HER2-targeted therapies such as trastuzumab have improved lifespans in women with HER2-positive early breast cancer, sparking interest in whether chemotherapy can be de-escalated. The PHERgain study examines whether it can be avoided entirely.
The primary endpoint results of the multicenter, open-label, noncomparative study were released in The Lancet Oncology in 2021.
Study methods and results
At 45 hospitals in Europe, patients with HER2-positive, stage I-IIIA, invasive, operable breast cancer were randomly assigned between 2017 and 2019 to receive chemotherapy prior to surgery (n = 71, group A) or to only receive hormone therapy with trastuzumab and pertuzumab, unless PET scans suggested they needed chemotherapy because they weren’t properly responding (n = 285, group B).
At a median follow-up of 5.7 months, 86 patients in the latter group had a pathological complete response and therefore met the first primary endpoint.
The new analysis tracked patients for 3 years after they underwent surgery (n = 63 and 267 for patients in groups A and B, respectively). As previously noted, at a median follow-up of 43.3 months (range, 2.4-63.0 months), only 1 of 86 patients in group B who didn’t receive chemotherapy had a recurrence of cancer (a locoregional ipsilateral recurrence). The 98.8% invasive disease–free survival rate was higher that what was seen for patients in group B as a whole (95.4% invasive disease–free survival, 95% CI, 92.8%-98.0%, P < .001). The 95.4% met the study’s second primary endpoint.
Treatment-related adverse events were higher in the group that received chemotherapy only (group A) versus group B (experiencing an adverse event grade of at least 3, 61.8% vs. 32.9%, respectively, P < .001; serious adverse events, 27.9% vs. 13.8%, respectively; P = .01). Those in group B who didn’t receive any chemotherapy had very few treatment-related adverse events that were considered being greater than a grade 3 (1.2%) and no treatment-related serious adverse events. The researchers reported that there were no treatment-related deaths.
In an interview, Kevin Kalinsky, MD, MS, an oncologist at Emory University Hospital, Atlanta, and cochair of the session where the study data was presented, said the “intriguing and meaningful [findings] highlight the fact that not everyone may need chemotherapy.” In the big picture, the results reflect a movement toward “individualized, personalized medicine, and moving away from one size fits all.”
Should clinicians embrace the study’s strategy, and what are the costs?
“There may be a need for additional evaluation in a large phase 3 trial,” Dr. Kalinsky said.
There was no discussion about cost during the ASCO presentation. However, Dr. Kalinsky noted that there will be cost savings if patients don’t need chemotherapy. But he added that insurers in the United States don’t always cover the PET scans that are needed to evaluate whether patients are responding to hormone therapy.
The study is funded by Roche and sponsored by MedSIR. Dr. Cortes has multiple disclosures, including stock/other ownership in Leuko, MedSIR, and Nektar and honoraria from AstraZeneca, Celgene, Daiichi Sankyo, Eisai, Lilly, Merck Sharp & Dohme, Novartis, Pfizer, Roche, and Samsung. Dr. Kalinsky has no disclosures.
