Generation of HER2-specific antibody immunity during trastuzumab adjuvant therapy associates with reduced relapse in resected HER2 breast cancer

Abstract

Background: Resected HER2 breast cancer patients treated with adjuvant trastuzumab and chemotherapy have superior survival compared to patients treated with chemotherapy alone. We previously showed that trastuzumab and chemotherapy induce HER2-specific antibodies which correlate with improved survival in HER2 metastatic breast cancer patients. It remains unclear whether the generation of immunity required trastuzumab and whether endogenous antibody immunity is associated with improved disease-free survival in the adjuvant setting. In this study, we addressed this question by analyzing serum anti-HER2 antibodies from a subset of patients enrolled in the NCCTG trial N9831, which includes an arm (Arm A) in which trastuzumab was not used. Arms B and C received trastuzumab sequentially or concurrently to chemotherapy, respectively.

Methods: Pre-and post-treatment initiation sera were obtained from 50 women enrolled in N9831. Lambda IgG antibodies (to avoid detection of trastuzumab) to HER2 were measured and compared between arms and with disease-free survival.

Results: Prior to therapy, across all three arms, N9831 patients had similar mean anti-HER2 IgG levels. Following treatment, the mean levels of antibodies increased in the trastuzumab arms but not the chemotherapy-only arm. The proportion of patients who demonstrated antibodies increased by 4% in Arm A and by 43% in the Arms B and C combined (p = 0.003). Cox modeling demonstrated that larger increases in antibodies were associated with improved disease-free survival in all patients (HR = 0.23; p = 0.04).

Conclusions: These results show that the increased endogenous antibody immunity observed in adjuvant patients treated with combination trastuzumab and chemotherapy is clinically significant, in view of its correlation with improved disease-free survival. The findings may have important implications for predicting treatment outcomes in patients treated with trastuzumab in the adjuvant setting.

Trial registration: ClinicalTrials.gov, NCT00005970 . Registered on July 5, 2000.

Keywords: Adaptive immune response; Disease-free survival; HER2 +; Trastuzumab.

Conflict of interest statement

Ethics approval and consent to participate

This study was approved by the Mayo Clinic Institutional Review Board with written informed consent. Consent to participate has been obtained.

Competing interests

The authors declare that they have no competing interests.

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Figures

Fig. 1

Trastuzumab induces anti-HER2 antibodies during adjuvant treatment of resected HER2+ BC patients. a shows the median time (gray bar) at which samples were collected post-treatment for each arm, calculated from the inset scatter dots each of which represents a unique sample from a unique patient. Inset colored bars show treatment timeline for each arm with the red bar representing adriamycin and cyclophosphamide (AC) therapy, the green bar paclitaxel, and the blue bar trastuzumab. P value was calculated using one-way ANOVA. b shows Kaplan-Meier analysis comparing disease-free survival (DFS) for each of the cohorts of patients from which samples were drawn. c-e show the individual changes in antibody levels given indicated as the relative index (RI) for Arms A-C of N9831, respectively. Each line is calculated from triplicate measurements for each pre- and post-treatment specimen. The inset blue dotted line represents the cutoff for what is considered a positive antibody level (see Materials and Methods). P values were calculated using the paired Student’s t test

Fig. 2

A high proportion of patients demonstrate elevated HER2-specific antibody responses following treatment with trastuzumab. a shows the mean (±s.e.m.) RI, both pre- and post-treatment for Arm A (N = 22) and Arm B and C combined (N = 28). P values for Arms A and B were calculated using the paired Student’s t test. b is a scatter plot comparing baseline RI with treatment-induced changes (ΔRI, y-axis) for patients who received chemotherapy plus trastuzumab. Each dot represents a unique patient in Arms B or C. c is a scatter plot comparing the time of post-treatment serum sample collection (x-axis) and the post-treatment change (i.e., ΔR) in antibody levels from baseline (y = axis). The inset lines, R value, and P value in Panels B and C represent linear regression analysis. d shows a bar graph of the proportion of patients who demonstrated a positive antibody response (defined as RI ≥0.2) before (Pre) and after treatment (Post). P values were calculated with a Fisher’s exact test

Fig. 3

Higher levels of post-treatment antibodies are associated with improved disease-free survival. Kaplan-Meier curve showing disease-free survival (DFS) in all patients (N = 50) with antibody changes of ≥0.2 RI units (inclusive of all arms) compared with patients that did not experience increased antibodies