Posted: Friday, June 16, 2023
A significant number of patients with early-stage, HER2-positive breast cancer treated with dual HER2 blockade—trastuzumab and pertuzumab—could likely omit chemotherapy from their regimens and have “substantial” 3-year invasive disease–free survival outcomes with less toxicity, according to an update from the open-label, phase II PHERGain trial. This trial’s novel adapted-response structure may assist oncologists in more accurately identifying patients who would likely be able to forgo chemotherapy throughout their treatment journey, according to Javier Cortés, MD, PhD, of the International Breast Cancer Center, Barcelona, and colleagues at the 2023 American Society of Clinical Oncology (ASCO) Annual Meeting (Abstract LBA506).
In this part of PHERGain, 285 patients with early-stage, HER2-positive disease received two cycles of trastuzumab and pertuzumab, followed by 18F-fluorodeoxyglucose-PET scans. Patients whose scans revealed that their breast lesions were reduced by at least 40% from baseline were considered PET responders. The 58 patients who were not PET responders began receiving chemotherapy as well as dual HER2 blockade; the other 227 patients, PET responders, continued the HER2 blockade but received no chemotherapy.
After six to eight cycles of therapy, 267 of the 285 patients underwent surgery and were assessed postoperatively for pathologic complete response. About one-third of the 227 PET responders (n = 86) achieved a pathologic complete response and did not receive chemotherapy for the rest of the study, whereas the other two-thirds did receive chemotherapy.
In the initial 227 PET responders, the 3-year invasive disease–free survival was 95.4%. In the 86-patient subset without chemotherapy, the 3-year invasive disease–free survival was 98.8%, with one patient ultimately experiencing regional recurrence.
Disclosure: The study authors’ disclosure information can be found at coi.asco.org.