The effectiveness of Neoadjuvant Hormone therapy in comparison with Neoadjuvant polychemotherapy in HR+ HER2- invasive Lobular Breast Cancer (single-center retrospective study)

Introduction. Patients with invasive lobular breast cancer are common candidates for preoperative therapy to reduce the size of the primary tumor and enable breast-conserving surgery. Most lobular carcinomas have the HR+HER2- molecular subtype. The significance of the lobular subtype as a predictive biomarker in the choice of systemic therapy, whether neoadjuvant hormonal therapy (NHT) or polychemotherapy (NCT), has not been studied.

Objective. The aim of this study is to evaluate the effectiveness of NHT compared to NCT among patients with lobular luminal HER2– breast cancer. 

Materials and Methods. We retrospectively assessed the treatment outcomes of 80 patients with HR+HER2- lobular breast cancer who received neoadjuvant systemic therapy (NHT or NCT) from January 1, 2015, to April 1, 2025, and were operated on at the State Budgetary Healthcare Institution “St. Petersburg Clinical Scientific and Practical Center for Specialized Types of Medical Care (Oncological) named after N. P. Napalkov”. We analyzed data on objective response rates (ORR) and breast-conserving surgery (BCS) rates in the two treatment groups.

Results. Among the 80 patients with HR+HER2– lobular breast cancer treated at GBUZ SPb KNPС SVMPO, 61.3% (n=49) received NHT and 38.8% (n=31) received NCT. No statistically significant differences in treatment responses were observed: partial response was 45.2% (n=14) in the NCT group vs. 51.0% (n=25) in the NHT group (p=0.61), stabilization was 54.8% (n=17) vs. 49.0% (n=24), respectively (p=0.61). All patients in the study underwent surgery: radical mastectomy was performed in 62.5% (n=50) and breast-conserving surgery in 37.5% (n=30). The rate of BCS in the NHT group was 46.9% (n=23), while in the NCT group it was 22.6% (n=7) (p=0.028, OR=3.03; 95% CI: 1.10–8.34). 

Conclusions. No statistically significant differences in response to preoperative therapy, whether NCT or NHT, were found among patients with lobular HR+HER2– breast cancer. However, it is important to note that with comparable treatment outcomes in our study, preoperative hormonal therapy appears to be a preferred option due to its lower toxicity. Additionally, we observed a trend towards a higher rate of breast-conserving surgeries in the NHT group. It is evident that our results have several significant limitations, primarily a small sample size due to the relative rarity of this subtype and the necessity for centralized assessment of tumor material. Secondly, the imbalance between the groups regarding the primary tumor size may also have influenced our results. Further research is required.