ABSTRACT
Background: Thymic epithelial tumors (TET) are rare malignancies associated with dysregulation of the immune system and humoral and cell mediated immunity abnormalities. Anti-syndrome coronavirus type 2 (SARS-CoV-2) vaccine is effective at preventing COVID-19 morbidity and mortality. No published data are available regarding the immunization in TET patients (pts). The aim of this study was to evaluate the immunization in TET pts who received two doses of mRNA vaccine, by longitudinal serological detection of SARS-COV-2 spike-binding IgG antibody. Methods: Starting from April 2021 to October 2021, consecutive TET pts referred to the Rare Tumors Coordinating Center of Campania Region (CRCTR - Naples, Italy) were enrolled. All study subjects received two doses of COVID-19 mRNA vaccine (BNT162b2 by Pfizer-BioNTech). SARS-CoV-2 spike-binding IgG antibody (Ab) serological levels were analyzed by centralized chemiluminescent immunoassay (CLIA) at different time-points, including before 1st vaccine dose (T0) and 1 month after 2nd dose (T2). Cut-off for Ab titers positivity was > 25 AU/mL. Results: Forty pts were enrolled;23 (57.5%) were female and 17 (42.5%) male. Eleven pts (27.5%) suffered from thymic carcinoma, 28 (70%) thymoma, and 1 (2.5%) thymic hyperplasia. At the time of study enrollment, 20 pts (50%) had no evidence of disease (NED) and were in followup;the remaining 20 pts had evidence of disease (ED) by imaging and were receiving systemic treatment (55% oral low-dose etoposide-based therapy, 40% somatostatin analogs + prednisone, 5% supportive care). Immune system disorders were diagnosed in 29 TET pts (72.5%): 19 pts (47.5%) had Good's Syndrome (GS) and 10 (25%) other immune disorders. At T0, all enrolled pts had negative Ab titers and no prior SARS-CoV-2 infection. At T2, Ab data were available for 37 pts (92.5%): 18 pts (48.7%) had positive Ab titers, whereas 19 (51.3%) did not achieve seroconversion. Among pts with ED, seroconversion was achieved only in 2 cases (11.8%). Lack of seroconversion at T2 was significantly associated with ED (Fisher's exact test p: 0.0001) and with the presence of GS (Fisher's exact test p: 0.0489). No significant association of seroconversion with other immune disorders and disease features was found. Conclusions: Our data showed that TET pts with ED had substantially higher probability of impaired seroconversion after SARS-COV-2 vaccine as compared with NED pts. We warrant further studies to evaluate the role of disease status, anti-tumor treatments and immune disorders in post-vaccine immunization of TET pts.