Anthracycline-free neoadjuvant therapy induces pathological complete responses by exploiting immune proficiency in HER2+ breast cancer patients

Abstract

Background: Neoadjuvant Chemotherapy (NC) including trastuzumab induces a high rate of pathological Complete Responses (pCR) in patients with locally advanced HER2-overexpressing Breast Cancer (BC), but is penalized by a severe cardiotoxicity when combined with anthracyclines. A phase II study was designed to assess whether an anthracycline-free NC regimen based on the early addition of trastuzumab to paclitaxel may increase the pCR rate without inducing severe cardiotoxicity in patients with locally advanced HER2-overexpressing BC. Immunomonitoring was performed to assess the contribution of patients' immunological background to the induction of clinical responses.

Methods: Stage II-III HER2-positive BC patients received 24 weeks paclitaxel and trastuzumab NC, followed by 1 year adjuvant trastuzumab ± hormonal and/or radio-therapy. Assessment of pCR rate was the primary endpoint. A group of HER2-negative BC patients treated with neoadjuvant taxanes and anthracyclines was included. Serum levels of 10 cytokines and the efficiency of trastuzumab-mediated antibody-dependent cell cytotoxicity (ADCC) were monitored in vitro every 3 months.

Results: From July 2006 to February 2013, we enrolled 109 patients including 46 evaluable HER2-positive cases. A pCR rate of 50% was reached and no severe cardiotoxicity occurred. Serum cytokine profiling revealed only an IL-10 decrease (P = 0.02) in patients achieving a partial response, while HER2-negative patients disclosed marked cytokines changes. Compared to the unfavourable F/F genotype, patients carrying the V allele in the FcγRIIIa-158 polymorphism showed a higher efficacy of trastuzumab-ADCC throughout treatment (P ≤0.05).

Conclusions: In the absence of anthracyclines, trastuzumab and paclitaxel induced a high rate of pCR, exploiting the synergy between the immunomodulating properties of these drugs and the retained immunological proficiency of patients with HER2-overexpressing BC.

Trial registration: Trial registration number: NCT02307227, registered on ClinicalTrials.gov (http://www.clinicaltrials.gov, November 26, 2014).

Figure 1

Disease-free survival and Overall survival. A. Disease-free survival and B. Overall survival in the HER2-positive group.

Figure 2

Serum cytokine profile. Interleukin (IL)-2, IL-12p70, IL-1α, IL-1β, IL-8, IL-6, IL10, and granulocyte-macrophage colony-stimulating factor (GM-CSF) levels were evaluated in serum samples from HER2-negative (n = 36) and HER2-positive (n = 25) patients at diagnosis, and at the 12° and 24° weeks (W) of NC treatment. A. Trend of cytokine levels throughout NC in the 2 groups of treatment. Box plots represent the median values, the 25th, and the 75th percentiles. B. IL-10 levels in HER2-positive patients achieving a complete (n = 13) or a partial (n = 12) pathological response. Each circle symbolizes the IL-10 concentration measured in each patient. The mean value is indicated. C. Cytokine levels in HER2-negative patients divided in individuals achieving a complete (n = 5) or a partial (n = 31) pathological response. Statistical analysis was performed with the Student’s t test; *P < 0.05. HER2, human epidermal growth factor receptor-2. HER2⁺, HER2-positive patients. HER2^-, HER2-negative patients.

Figure 3

Monitoring of Trastuzumab-mediated ADCC activity in HER2-positive patients according to the FcγRIIIa polymorphism. Representative data obtained against the HER2-overexpressing cell line MDA-MB-453 using patients’ PBMCs collected at diagnosis, and at the 12° and 24° weeks (W) of NC treatment. A. Data were classified by the V/V (n = 9), V/F (n = 17), and F/F (n = 10) genotypes of the FcγRIIIa polymorphism. Statistical analysis was performed with the Kruskal-Wallis test. B. Analysis was performed comparing V carriers (n = 26) with F/F individuals, through the Wilcoxon test. Graphs on the left show the absolute percentage of lysis measured at a 30:1 Effector:Target ratio. Natural Killer (NK) cells were identified in flow cytometry as CD3-CD16 + CD56dim lymphocytes. Histogram plots on the right display normalized lysis calculated for 10,000 NK cells. Data are represented as means and standard deviations. The Student t test was employed for NK cells percentage variations. *Chi-square or |Z| < 0.05. **P < 0.05. HER2, human epidermal growth factor receptor-2.