OBJECTIVES: Given their inclusion and exclusion criteria, randomized clinical trials (RCT) might not include a population that truly mirrors real life (RL). This raises concerns about the applicability of RCT results in clinical practice. We evaluated the efficacy of anti-HER2 treatment with pertuzumab combined with trastuzumab and a taxane as first-line treatment for HER2-positive metastatic breast cancer in a RL setting, and compared the safety results obtained in our population versus the experimental cohort of the CLEOPATRA RCT, which led to the approval of this therapy.MATERIALS AND METHODS: Patients treated with trastuzumab, pertuzumab and a taxane were enrolled in this retrospective study. We compared the tumor features and the patients' characteristics of the RL cohort to those of the CLEOPATRA cohort. We also compared the median progression-free survival (PFS) in the RL population versus specific patients' subgroups.RESULTS: RL patients were more frequently HR-positive, less likely to have visceral metastases (P <.001 for both) and had more frequently received (neo)adjuvant hormone therapy or trastuzumab than CLEOPATRA patients (P = .004 and P <.001, respectively). The median number of anti-HER2 cycles was 8 vs 24 and the median number of cycles was 7 vs 8 for docetaxel in the RL versus CLEOPATRA population, respectively. Adverse reactions of all grades were less frequent in RL. Median PFS was 27.8 months in the RL population and the treatment was equally effective in all patients' subgroups.CONCLUSION: This study provides compelling evidence that pertuzumab, trastuzumab and a taxane are effective and safe also in a clinical scenario.