Multicenter real-world study of trastuzumab combined with pirotinib or pertuzumab as a neoadjuvant therapy for stage II-III HER-2 positive breast cancer.

e12609 Background: Neoadjuvant therapy is an important treatment strategy for HER-2 positive early breast cancer and Trastuzumab combined with Pertuzumab (HP) plus chemotherapy is the current standard treatment scheme. In recent years, multiple studies have revealed that the combination of Trastuzumab and Pyrotinib (HPy) has satisfactory efficacy and controllable toxic side effects. In clinical practice, how to choose a target regimen (HP or HPy) for HER-2 positive breast cancer patients is one of the key problems to be solved urgently. Methods: In this prospective, multicenter, observational real-world study (ChiCTR220056467), patients with stage II-III HER-2 positive breast cancer were assigned to the HP group or the HPy group according to the doctor's recommendation and their own wishes (specific programs include: 6 * TCbHP/6 * TCbHPy, 4 * EC-4 * THP/4 * EC-4 * THPy and 6 * THP/6 * THPy). The primary endpoint was total pathological complete response rate (tpCR, ypT0/isypN0), while the secondary endpoints were safety indicators, EFS and OS. Results: From January 2022 to December 2024, 687 patients from 10 hospitals were enrolled in the real-world study. As of now, 386 patients have completed neoadjuvant therapy and surgery with complete data, including 204 in the HP group and 182 in the HPy group, respectively. Statistical difference were observed in neoadjuvant chemotherapy and the expression levels of Ki-67. To reduce selection bias and ensure comparability of baseline data between two groups, propensity score matching (PSM) was performed in a 1:1 ratio. After PSM, 136 patients were equally divided and there was no statistically significant difference in baseline characteristic between the two groups. Before PSM, there was a statistically significant difference in tpCR rates between the HP group and the HPy group (63.24% vs 48.35%, P = 0.003); After PSM, the tpCR rate of the HPy group was consistent with that of the HP group, with no statistically significant difference (60.29% vs 61.76%, P = 0.860). Subgroup analysis showed that there was no statistically significant difference in tpCR rates between the HPy group and the HP group in each subgroup (all P interactions > 0.05). In terms of safety, 386 cases were included in the analysis, among which the most common adverse reactions in the HPy group were diarrhea (82.7%), nausea (80.4%), and vomiting (78.1%), while the most common adverse reactions in the HP group were anemia (66.7%), vomiting (55.9%), and leukopenia (49.3%). Conclusions: In the real-world study, HER-2 positive early breast cancer patients are more likely to use HP as neoadjuvant therapy, and HP are more likely to be used in combination with platinum drugs. Our study has confirmed that there is no significant difference in tpCR rates between HPy or HP. Clinical trial information: ChiCTR220056467 .