Some patients with HER2-positive early breast cancer can safely forgo neoadjuvant chemotherapy, according to findings presented at the ASCO Annual Meeting 2023.

About 1 in 3 patients who were assigned to receive neoadjuvant trastuzumab and pertuzumab, with or without endocrine therapy (ET), were able to skip chemotherapy safely, said study presenter Javier Cortés, MD, PhD, of the International Breast Cancer Center in Barcelona.

These results come from the phase 2 PHERGain trial ( Identifier: NCT03161353), which included 356 patients with stage I-IIIA, HER2-positive breast cancer.

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Patients were randomly assigned to receive trastuzumab and pertuzumab with chemotherapy (n=71) or without it (n=285). Patients in the no-chemotherapy arm also received ET (letrozole or tamoxifen) if they had hormone receptor-positive disease.

Patients in the chemotherapy arm received trastuzumab, pertuzumab, docetaxel, and carboplatin for 6 cycles, underwent surgery, and received adjuvant trastuzumab and pertuzumab (with or without ET) for 12 cycles.

Among patients in the chemotherapy-free arm, those who had a response by PET after 2 cycles received another 6 cycles of trastuzumab and pertuzumab, with or without ET, before surgery. Patients without a PET response switched therapy and received 6 cycles of chemotherapy with trastuzumab and pertuzumab before surgery.

Patients in the chemotherapy-free arm who had a pathologic complete response (pCR) after surgery could continue on the same treatment for 10 cycles. Patients without a pCR were switched to 6 cycles of chemotherapy with trastuzumab and pertuzumab, followed by 4 cycles of trastuzumab and pertuzumab, with or without ET.

In the chemotherapy-free arm, 79.6% of patients were PET responders and could continue on the chemotherapy-free regimen (227/285). Of these patients, 37.9% had a pCR after surgery. pCR among PET responders was the study’s first primary endpoint.

Among all patients initially assigned to the chemotherapy-free arm, the 3-year invasive disease-free survival (iDFS) rate was 95.4%. This met the study’s second primary endpoint, as less than 15 patients had iDFS events. Of the 12 patients with iDFS events, 11 patients had disease relapse, and 1 died without recurrence.

Dr Cortés noted that this study was not designed to directly compare the treatment arms. Still, the 3-year iDFS rate was 98.8% in patients who never received chemotherapy and 98.3% in patients who were assigned to chemotherapy upfront.  

The 3-year distant disease-free survival rate was 98.3% in patients assigned to chemotherapy upfront, 96.5% in patients assigned to the chemotherapy-free arm, and 100% in patients who never received chemotherapy. The 3-year overall survival rate was 98.4%, 98.5%, and 100.0%, respectively.

Grade 3-4 treatment emergent adverse events occurred in 64.7% of patients assigned to chemotherapy, 41% of patients assigned to the chemotherapy-free arm, and 12.8% of patients who did not receive chemotherapy.

Disclosures: This research was supported by MedSIR and Roche. Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


Cortés J, Pérez-García JM, Ruiz-Borrego M, et al. 3-year invasive disease-free survival (iDFS) of the strategy-based, randomized phase II PHERGain trial evaluating chemotherapy (CT) de-escalation in human epidermal growth factor receptor 2-positive (HER2[+]) early breast cancer (EBC). ASCO 2023. June 2-6, 2023. Abstract LBA506.