Pyrotinib in the treatment of women with advanced HER2 positive breast cancer: A multicenter, prospective, real-world study.

e13012 Background: Pyrotinib is a newly-developed irreversible pan-ErbB receptor tyrosine kinase inhibitor. The efficacy of pyrotinib in patients with different baseline characteristics in the actual clinical practice has been rarely reported. This study analyzed the efficacy and safety of pyrotinib in the real world. Methods: Patients with histologically confirmed advanced HER2 positive breast cancer were included in the analyses. All patients received pyrotinib-based therapy were given pyrotinib once a day in a 21-day cycle. The primary endpoint was progression-free survival (PFS). Secondary endpoints included adverse events (AE), objective response rate (ORR), disease control rate (DCR), and overall survival (OS). Results: A total of 132 patients (median age: 52 years [29-78]) were enrolled from February 2019 to March 2020. 94(71.21%) patients had visceral metastatic lesions and 20 (15.15%) had brain metastases. HR+, HR-, or unknown HR status for primary tumor accounted for 56.82%, 42.42%, 0.76%, respectively. 115(87.12%) patients were previously administered with trastuzumab. 96(72.73%) patients received pyrotinib-based therapy as a second or further line of treatment. 94(71.21%) patients initiated pyrotinib treatment at 400 mg. Treatment regimens were pyrotinib plus capecitabine (55.30%), pyrotinib combined with trastuzumab (18.18%), and pyrotinib monotherapy (8.33%), pyrotinib combined with endocrine therapy, radiotherapy or antiangiogenic drugs (3.79%). A total of 132 patients were included in PFS analysis. mPFS was 12.0 months (95%CI 8.1-18.8). mPFS for patients without primary trastuzumab-resistant breast cancer was 14.1 months (95%CI 8.7-23.3). Patients receiving pyrotinib-based therapy as their ≥3 lines treatment had lower mPFS than those receiving pyrotinib-based therapy as their < 3 lines treatment (8.8 vs. 15.1 months, P= 0.119). mPFS in patients receiving regimen with and without capecitabine were 15.1 months and 8.4 months, respectively ( P= 0.081). As of data cutoff, mOS has not yet been reached. Among the 65 patients available for efficacy evaluation, 1 (1.54%) patient achieved complete response (CR), 24 (36.92%) patients had partial response (PR), 30 (46.15%) patients achieved stable disease (SD), and 10 (15.38%) patients had progression disease (PD), resulting in an ORR of 38.46% and DCR of 84.62%. The most common AE was diarrhea (84.17%), but only 5 (4.17%) patients were reported grade ≥ 3 diarrhea which could be well controlled. Other AEs with an incidence higher than 20.00% were anemia (36.67%), leukopenia (25.83%), vomiting (25.00%), neutropenia (22.50%). No treatment-related death occurred. Conclusions: Pyrotinib demonstrated an encouraging efficacy and manageable safety in patients with advanced HER2+ breast cancer. More data would be analyzed and reported in the future. Clinical trial information: ChiCTR1900021819.