Impaired seroconversion after SARS-CoV-2 mRNA vaccine in patients with thymic epithelial tumors

INTRODUCTION: Thymic epithelial tumors (TETs) are rare malignancies associated with dysregulation of the immune system and humoral and cell mediated immunity abnormalities. Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) mRNA vaccine is effective in preventing COVID-19 morbidity and mortality. The aim of this study was to evaluate the seroconversion in TET patients after two doses of mRNA vaccine. METHODS: This is a prospective study where consecutive TET patients were enrolled before receiving the first dose of SARS-CoV-2 mRNA vaccine (BNT162b2 by Pfizer-BioNTech). SARS-CoV-2 spike-binding IgG antibody (Ab) serological levels were analyzed at different time-points, including before first vaccine dose (T0), 1 month after 2(nd) dose (T2) and 3 months after 2(nd) dose (T3). RESULTS: Overall, 39 patients were included in the analysis. All patients had negative Ab titers at T0. Nineteen (48.7%) patients were in follow-up with no residual tumor lesion/s [referred as no evidence of disease (NED)], and 20 (51.3%) had evidence of disease (ED) and were receiving systemic treatment. Dysregulations of the immune system were diagnosed in 29 patients (74.4%) with Good’s Syndrome (GS) being the most frequent immune disorder (48.7 %). At univariate analysis lack of seroconversion at T2 was significantly associated with ED (p<0.001) and with GS (p= 0.043). A significant association with impaired seroconversion was confirmed at multivariate analysis for ED p=0.00101 but not for GS (p= 0.625). CONCLUSIONS: Our data showed that TET patients with ED had substantially higher probability of impaired seroconversion after SARS-CoV-2 mRNA vaccine as compared with NED patients.