Özet:

It is known that the addition of Trastuzumab to neoadjuvan treatment in breast cancer increases the rate of pathological full response (PTY). However, there are limited data on the order of use of trastuzumab. We aimed at examining whether the neoadjuvan trastuzumab application order in the HER2 positive local advanced breast cancer has an effect on PTY. The data of patients who used neoadjuvan trastuzumab due to HER2 positive stage 2 and 3 breast cancer between 2010 and 2018 were retrospective examined and 30 patients who received trastuzumab after anthracycline-based treatment and 16 patients who received treatment with a reverse ranking were taken to study. Results: A total of 46 patients were taken to the study and the median follow-up period was 31 months (December; 7-98). The average age of patients was 51 years (19-72). 52% of all patients were postmenopausal and 67% hormone receptors positive. All patients had a clinical nod positive and 54% were cN1. Patients were separated by the group according to the tractuzumab ranking. There was no difference between the groups in terms of basic characteristics. The PTY ratio was 63% in those who started treatment with trastuzumab and 37% in the other group (p=0.1). The three-year cumulative survival rates were 100% and 80% respectively (p=0.2). In one-variable analysis, the PTY ratio was significantly higher in the group with stage 2 and body mass index (BMI) <25 kg/m2. In the multi-variable analysis, it was found that only VKI <25 kg/m2 was an independent predictive factor (Odds ratio: 18.1; 95% Confidence range 1.39-36.0, p=0.03). The start of the treatment with trastuzumab increased the PTY rate numerically, but the difference was not statistically meaningful. The reason that the difference is not statistically meaningful may be that the number of patients is low. Prospective studies are needed for the relationship of the Trastuzumab ranking with PTY with a larger patient population. Keywords: Breast cancer; Neoadjuvan treatment; Trastuzumab ranking; Patological complete response ABSTRACT Aim: The aim of this study was to investigate the effect of neoadjuvant trastuzumab administration order on PCR in locally advanced breast cancer. Material and Method: The data of patients who had recieved neoadjuvant trastuzumab for HER 2 positive stage 2 and 3 breast cancer between 2010 and 2018 were retrospectively analyzed; 30 patients who first had received anthracycline treatment then trastuzumab and 16 patients who had received in reverse order included to our study. Results: A number of 46 patients included study and median follow-up time was 31 months (range; 7-98). The median age of the whole group was 51 years (19-72). There was no significant difference in basal characteristics when the patients were grouped according to the order of trastuzumab. PCR rates were 63% in patients whose treatment had started with trastuzumab, 37% in the other group (p=0. 1) and the 3-year cumulative disease-free survival rates were 100% and 80%, respectively (p=0.2). In the univariate analysis, the PCR ratio was significantly higher in stage 2 and BMI<25 kg/m2 group; in multivariate analysis, only having a BMI<25 kg/m2 was found to be an independent predictive factor (Odds ratio: 18.1; 95% CI 1.39-36.0, p=0.03). Conclusion: Although starting neoadjuvant therapy with trastuzumab increased the rate of PCR numerically, the difference was not statistically significant. The reason of not achieving statistical significance may be the insufficient number of patients. Prospective trials are needed to assign the treatment sequence that may affect PCR. Keywords: Breast cancer; Neoadjuvant treatment; Trastuzumab sequencing; Pathologic complete response