Impact of adding pertuzumab to trastuzumab plus chemotherapy in neoadjuvant treatment of HER2 positive breast cancer patients: a multicenter real-life HER2PATH study.

AIM: To investigate the pathological complete response (pCR) achieved after neoadjuvant therapy with versus without adding pertuzumab (P) to trastuzumab (H) plus neoadjuvant chemotherapy (NCT) in HER2+ breast cancer (BC) patients in a real-life setting. METHODS: A total of 1528 female HER2+ BC patients who received NCT plus H with or without P were included in this retrospective real-life study. Primary endpoint was pCR rate (ypT0/Tis ypN0). Clinicopathological characteristics, event-free survival (EFS) time, and relapse rates were evaluated with respect to HER2 blockade (NCT-H vs. NCT-HP) and pCR. RESULTS: Overall, 62.2% of patients received NCT-H and 37.8% received NCT-HP. NCT-HP was associated with a significantly higher pCR rate (66.4 vs. 56.8%, p < 0.001) and lower relapse (4.5 vs. 12.2%, p < 0.001) in comparison to NCT-H. Patients with pCR had a significantly lower relapse (5.6 vs. 14.9%, p < 0.001) and longer EFS time (mean(SE) 111.2(1.9) vs. 93.9(2.7) months, p < 0.001) compared to patients with non-pCR. Patients in the NCT-HP group were more likely to receive docetaxel (75.0 vs. 40.6%, p < 0.001), while those with pCR were more likely to receive paclitaxel (50.2 vs. 40.7%, p < 0.001) and NCT-HP (41.5 vs. 32.1%, p < 0.001). Hormone receptor status and breast conservation rates were similar in NCT-HP vs. NCT-H groups and in patients with vs. without pCR. Invasive ductal carcinoma (OR, 2.669, 95% CI 1.596 to 4.464, p < 0.001), lower histological grade of the tumor (OR, 4.052, 95% CI 2.446 to 6.713, p < 0.001 for grade 2 and OR, 3.496, 95% CI 2.020 to 6.053, p < 0.001 for grade 3), lower T stage (OR, 1.959, 95% CI 1.411 to 2.720, p < 0.001) and paclitaxel (vs. docetaxel, OR, 1.571, 95% CI 1.127 to 2.190, p = 0.008) significantly predicted the pCR. CONCLUSIONS: This real-life study indicates that adding P to NCT-H enables higher pCR than NCT-H in HER2+ BC, while pCR was associated with lower relapse and better EFS time.