Abstract P3-23-01: Antibody responses after SARS-CoV-2 mRNA vaccination in breast cancer patients
Authors: Chumsri Saranya , Advani Pooja P. , Pai Tanmayi S , Li Zhou , Acampora Marites , Reynolds Gina A , Moreno-Aspitia Alvaro , Marquez Christopher P , Knutson Keith L. 
Published: March 2022

Abstract
Background: SARS-CoV-2 mRNA vaccines have been demonstrated to have robust and durable humoral immune response in healthy individuals. However, their effectiveness in immunocompromised patients, particularly cancer patients, remains less known. Newer data suggests that cancer patients may not mount adequate protective immune response after vaccination. Methods: A retrospective study of patients ≥ 18 years old who had SARS-CoV-2 spike antibody (anti-S Ab) testing after 2 doses of SARS-CoV-2 mRNA vaccines between 12-90 days at Mayo Clinic between January 1, 2021 and May 10, 2021 was performed. The Elecsys Anti-SARS-CoV-2 S electrochemiluminescence immunoassay (Roche Diagnostics, Switzerland) was used to measure the antibody response. Patients with prior COVID-19 infection and patients on immunosuppressive therapy for an indication other than cancer were excluded. Categorical variables were summarized as frequencies (percentages) and continuous variables were reported as median with range. Wilcoxon signed rank test was used to compare continuous variables between groups and Chi-squared or Fisher’s exact test was used to compare categorical variables. All tests were two-sided with p value &lt; 0.05 considered statistically significant. The analysis was done using R program version 3.6.2. Results: Among 201 patients, 79 had breast cancer, 91 had a hematologic malignancy, 6 had other solid malignancies, and 25 had no history of cancer. All breast cancer patients on endocrine therapy or trastuzumab ± pertuzumab without chemotherapy (n=35) had anti-S Ab titer ≥ 500 U/mL. Patients on cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) appeared to have low level of anti-S Ab with 28.6% (n=4/14) had anti-S Ab titer ≤ 500 U/mL. Patients on chemotherapy also had low levels of anti-S Ab with 47% (n=14/30) having anti-S Ab titers ≤ 500 U/mL. When combining breast cancer patients on endocrine therapy alone or anti-HER2 therapy with patients without history of cancer as an immunocompetent group, there was significantly greater proportion of immunocompetent patients (97%) who had anti-S Ab titer ≥ 500 U/mL compared with only 8% of patients with hematologic malignancy and 55% of patients with solid malignancy on chemotherapy or CDK4/6i (p &lt; 0.001). Using multivariate logistic regression analysis adjusted for age, gender, and vaccine type, patients with solid malignancies and treatment-related cytopenia, including chemotherapy and CDK4/6i, (OR 35.51 [95%CI 8.38-255.25, p &lt; 0.001]) were more likely than immunocompetent patients to have a suboptimal anti-S Ab results ≤ 500 U/mL.Conclusion: A significant number of breast cancer patients on chemotherapies and CDK4/6i had poor humoral responses after SARS-CoV-2 mRNA vaccination. While CDK4/6i is not commonly considered as immunosuppressive therapy, breast cancer patients on CDK4/6i appeared to have suboptimal response to SARS-CoV-2 mRNA vaccine. Our study also highlights the significance of assessing antibody response after COVID-19 vaccines in these vulnerable patients.
Citation Format: Saranya Chumsri, Pooja P. Advani, Tanmayi S Pai, Zhou Li, Marites Acampora, Gina A Reynolds, Alvaro Moreno-Aspitia, Christopher P Marquez, Keith L. Knutson. Antibody responses after SARS-CoV-2 mRNA vaccination in breast cancer patients [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-23-01.