Anthracycline-Free Neoadjuvant Treatment in Patients with HER2-Positive Breast Cancer: Real-Life Use of Pertuzumab, Trastuzumab and Taxanes Association with an Exploratory Analysis of PIK3CA Mutational Status.

HER2 is considered one of the most traditional prognostic and predictive biomarkers in breast cancer. Literature data confirmed that the addition of pertuzumab to a standard neoadjuvant chemotherapy backbone (either with or without anthracyclines), in patients with human epidermal growth factor receptor 2 (HER2)-positive early breast cancer (EBC), leads to a higher pathological complete response (pCR) rate, which is known to correlate with a better prognosis. In this retrospective analysis, 47 consecutive patients with HER2-positive EBC received sequential anthracyclines and taxanes plus trastuzumab (ATH) or pertuzumab, trastuzumab and docetaxel (THP). Despite the limited sample size, this monocentric experience highlights the efficacy (in terms of pCR) and safety of THP in the neoadjuvant setting of HER2-positive EBC as an anthracycline-free approach. Given the role of PIK3CA as a prognostic and therapeutic target in breast cancer, tumors were also analyzed to assess the PIK3CA mutational status. Thirty-eight out of forty-seven patients were evaluated, and PIK3CA variants were identified in 21% of tumor samples: overall, one mutation was detected in exon 4 (2.6%), two in exon 9 (5.3%) and four in exon 20 (10.5%). Of note, one sample showed concurrent mutations in exons 9 (codon 545) and 20 (codon 1047). Among patients reaching pCR (n = 13), 38.5% were PIK3CA mutants; on the other hand, among those lacking pCR (n = 25), just 12% showed PIK3CA variants. Regarding THP-treated mutant patients (n = 5), 80% reached pCR (three hormone-receptor-negative, one hormone-receptor-positive). Interestingly, the only patient not achieving pCR had a tumor with two co-occurring PIK3CA mutations. In conclusion, this study provides new evidence about the efficacy and good safety profile of THP, compared to the ATH regimen, as an anthracycline-free neoadjuvant treatment of HER2-positive EBC. Further studies on larger/multicentric cohorts are planned for more in-depth analysis to confirm our molecular and clinical results.