CHICAGO – Targeted neoadjuvant therapy with trastuzumab emtansine (T-DM1) had similar efficacy with less toxicity, compared with a standard chemotherapy–based regimen for patients with HER2- and hormone receptor–positive breast cancers in the phase 2 Swedish .
The pathologic complete response (pCR) rate was 45% among 98 participants who were randomized to received T-DM1, and 47% in those randomized to receive docetaxel, trastuzumab, and pertuzumab (DTP),, reported at the annual meeting of the American Society of Clinical Oncology.
The pCR rate in hormone receptor(HR) –positive tumors was 36% in both groups, and the rates in HR-negative tumors were 59% and 67% in the T-DM1 and DTP arms, respectively; any differences in pCR rates between the groups were not statistically significant, said Dr. Bergh of the Karolinska Institute and University Hospital, Stockholm.
Patients were adults with HER2-positive breast cancer and tumor size greater than 20 mm or verified lymph node metastases at enrollment, and 62.6% of tumors were HR positive. Both treatment arms received their assigned therapy every 3 weeks for a planned total of six courses, but the protocol allowed a switch to the competing treatment upon progression, lack of response, or drug-related severe toxicity. All received postoperative epirubicin+cyclophosphamide every 3 weeks, with the T-DM1 arm receiving 4 courses and the DTP arm receiving 2 courses, and both arms also received adjuvant trastuzumab for 11 courses.
Age (median of 52 years), menopausal status, and histological type and grade were well balanced between the treatment groups.
Grade 3/4 adverse events occurred on 63 occasions in the DTP arm, compared with 10 in the T-DM1 arm; febrile neutropenia accounted for 26 and 3 of the events in the groups, respectively. All events, with the exception of liver toxicity, occurred more frequently in the DTP arm, Dr. Bergh said.
Ultimately, 9 patients switched from T-DM1 to DTP – 7 for progression or lack of response and 2 because of toxicity, and 18 switched from DTP to T-DM1 because of either progression or lack of response, and 14 because of toxicity. One patient in each group achieved pCR after switching, he noted.
“There was clearly better quality of life [during the study] for the T-DM1 group,” he added, noting that the quality of life data wereseparately at the meeting.
Additionally, an exploratory analysis demonstrated an early steep decrease of F-FDG uptake, suggesting that PET/CT may be a useful tool for predicting pCR.
Although neoadjuvant therapy produces high pCR rates and is the standard of care in HER2 positive breast cancer, the optimal treatment regimen remains to be established; but the current findings, along with prior data showing efficacy with T-DM1 in patients who fail to respond to two or more lines of anti-HER2 therapies, suggest it is a potential new standard for neoadjuvant therapy, particularly for patients with HER2- and HR-positive disease, he concluded.
Dr. Bergh reported a financial relationship with UpToDate, and research funding to his institution from Amgen, AstraZeneca, Bayer, Merck, Pfizer, Roche, and Sanofi.
SOURCE: Bergh J et al. ASCO 2019,