Real-world effectiveness of dual HER2 blockade with pertuzumab and trastuzumab for neoadjuvant treatment of HER2-positive early breast cancer (The NEOPETRA Study).

Purpose: Neoadjuvant clinical trials with dual HER2 blockade with pertuzumab and trastuzumab plus chemotherapy demonstrated high rates of pathological complete response (pCR) in HER2-positive early breast cancer (BC). We investigated whether the benefit on pCR seen in clinical trials is confirmed in a real-world setting.

Methods: Multicenter, retrospective study in patients with HER2-positive early BC receiving neoadjuvant treatment with pertuzumab and trastuzumab in routine clinical practice (n = 243). The primary endpoint was total pCR (tpCR) (ypT0/is ypN0).

Results: A total of 243 evaluable patients were included. Pertuzumab and trastuzumab were combined with anthracyclines and taxanes in 74.1% of patients, with single-agent taxane in 11.1% of patients and with platinum-based chemotherapy (CT) in 14.4% of patients. The tpCR rate was 66.4%:71% with anthracyclines and taxanes, 59.3% with single-agent taxane, and 48.6% with platinum-based combinations. The tpCR rate was higher among patients with hormone receptor (HR)-negative tumors (80.9%) vs HR-positive tumors (55.4%) (p < 0.001). A pCR in the breast (ypT0/is) was achieved in 67.6% of patients. Of 143 patients who showed radiological complete response (rCR) (62%), 112 (78.3%) patients also achieved tpCR. Assessment of rCR by magnetic resonance imaging (MRI) showed the highest negative predictive value (NPV) for predicting tpCR (83.5%). Breast-conserving surgery was performed in 58.7% of patients. Grade 3 and grade 4 toxicities were reported in 33 (18.2%) and 12 (6.6%) patients, respectively. No toxicity leading to death was reported.

Conclusions: This real-world analysis shows that neoadjuvant pertuzumab, trastuzumab, and chemotherapy achieve comparable or even higher rates of tpCR than those seen in clinical trials. The pCR benefit is higher in HR-negative tumors. The assessment of rCR by MRI showed the highest ability for predicting pCR. In addition, this neoadjuvant strategy confers an acceptable safety profile.