Evaluation of factors predicting pathologic complete response in locally advanced HER2 positive breast cancer treated with neoadjuvant pertuzumab, trastuzumab and chemotherapy; Real life data.

Purpose: Recently, neoadjuvant treatment approach has gained importance in locally advanced HER-2 positive breast cancer. Adding pertuzumab increases pathological complete response (pCR). In this study, we aimed to examine the clinicopathologic features that predict the pCR in patients receiving neoadjuvant pertuzumab, trastuzumab, and chemotherapy in locally advanced HER2 positive breast cancer.

Methods: Locally advanced HER2 positive breast cancer patients who were followed up in 4 different oncology centers and received 4 cycles of pertuzumab, trastuzumab and taxane were retrospectively evaluated. A total of 58 (92%) patients received anthracycline chemotherapy before combination of dual her-2 blockade and taxanes. Fisher's and chi-square tests were used for nominal variables and numeric data analyses.

Results: A total of 63 female patients were included in the study. Their median age was 46 years (21-75) and 40 (63.5%) patients were premenopausal. Median tumor size was 25 mm (2-70) and there were 22 (34.9%) patients with Stage 3a. pCR was 66% and 75% in the whole group and in the hormone negative group, respectively. Statistically significant increase was found in pCR in patients with grade 3 tumors and cerbB2 with 3+ immunohistochemical staining. No relationship was found between pCR and age at diagnosis, menopausal status, tumor infiltrating lymphocyte, dose-dense anthracycline, Ki67≥40, body mass index (BMI) ≥ 30 kg/m2 and accompanying DCIS.

Conclusion: Four cycles of pertuzumab, trastuzumab and taxane after neoadjuvant anthracycline for locally advanced HER2 breast cancer are associated with increased pCR in patients with grade 3 tumors and high cerbB2 expression.