ABSTRACT
PURPOSE: HER2-targeted therapies have dramatically improved outcomes of patients with HER2-positive breast cancer (BC), as demonstrated in neoadjuvant trials. This study aims to provide real-world evidence on the use and effectiveness of combined pertuzumab, trastuzumab and chemotherapy (CT) in early-stage HER2-positive BC. METHODS: A retrospective, multicentre study was conducted on patients diagnosed with HER2-positive early BC treated with neoadjuvant pertuzumab and trastuzumab plus CT at 13 Spanish sites. The primary endpoint was pathological complete response (pCR). RESULTS: A total of 310 patients were included. Pertuzumab and trastuzumab were combined with anthracyclines and taxanes, carboplatin and docetaxel, and taxane-based CT in 77.1%, 16.5%, and 6.5% of patients, respectively. Overall, the pCR rate was 62.2%. The pCR was higher amongst patients with hormone receptor-negative tumours and with tumours expressing higher levels of Ki-67 (> 20%). After postoperative adjuvant treatment, 13.9% of patients relapsed. Those patients who did not achieve pCR, with tumours at advanced stages (III), and with node-positive disease were more likely to experience distant relapse. Median overall survival (OS) and distant disease-free survival (D-DFS) were not reached at the study end. The estimated mean OS and D-DFS times were 7.5 (95% CI 7.3-7.7) and 7.3 (95% CI 7.1-7.5) years, respectively (both were significantly longer amongst patients who achieved pCR). Grade 3-4 anti-HER2 related toxicities were reported in six (1.9%) patients. CONCLUSION: Neoadjuvant pertuzumab and trastuzumab plus CT achieve high pCR rates in real-life patients with HER2-positive early BC, showing an acceptable safety profile. Innovative adjuvant strategies are essential in patients at high risk of distant disease recurrence.