De-escalated neoadjuvant therapy with nanoparticle albumin-bound paclitaxel and trastuzumab for low-risk pure HER2 breast cancer.

Purpose: Neoadjuvant trastuzumab combined with anthracycline and taxane is now considered a standard regimen for human epidermal growth factor receptor 2 (HER2)-positive breast cancer. A less toxic, non-anthracycline regimen has been considered as a treatment option for patients with node-negative small tumors. Estrogen receptor-negative and HER2-positive (pure HER2) tumors are more likely to achieve a pathological complete response (pCR). This study evaluates the activity and safety of neoadjuvant nanoparticle albumin-bound paclitaxel (nab-PTX) plus trastuzumab for pure HER2 breast cancer in patients with low risk of relapse.

Methods: We treated patients with tumors measuring ≤ 3 cm, node-negative, pure HER2 breast cancer using neoadjuvant nab-PTX 260 mg/m2 with trastuzumab every 3 weeks for four cycles. The primary endpoint was the pCR rate. The secondary endpoints included the clinical response rate, disease-free survival, pathologic response rate (defined as pCR or minimal residual invasive disease only in the breast), breast-conserving surgery conversion rate, safety, and disease-free survival. Depending on the pathological findings of surgical specimens, the administration of adjuvant anthracycline could be omitted.

Results: Eighteen patients were enrolled. No patient required dose delays or reductions; none showed disease progression, and all patients underwent surgery as scheduled. Of the 18 patients, 66.7% achieved pCR, and the adjuvant anthracycline regimen was omitted for all patients. The incidence of severe adverse events was quite low.

Conclusion: This less toxic, anthracycline-free regimen appears to be a significantly effective neoadjuvant therapy for patients with pure HER2 breast cancer at low relapse risk.