Evaluation of the effects of anticancer treatments in cancer patients undergoing SARS-COV2 vaccination (VAX-on study: Breast cancer subgroup analysis)

ABSTRACT

Background: Since the beginning of the covid19 pandemic, clinical and demographic data showed that cancer patients are at high risk of developing severe consequences of Sars-Cov2 disease. For this reason, vaccination is strongly recommended, especially for patients on active treatment. Nevertheless, the efficacy of the Sars-Cov2 vaccine in cancer patients is not fully investigated. Our trial aim to explore the seroconversion in a large series of vaccinated cancer patients undergoing active treatment. Here we present a subgroup analysis concerning patients affected by breast cancer. Methods: The "VAX-on" is a single-center study that enrolled 366 cancer patients who underwent oncological treatment within the last six months. The study was approved by the ethics committee and all patients had to sign specific informed consent to be enrolled. Subjects were vaccinated against Sars-Cov2 with mRNA vaccine BNT162b2 (Comirnaty)-Pfizer BioNTech. Blood samples were obtained to quantify the production of specific anti-Spike IgG antibodies at day 21 from the first dose and at 6-8 weeks after the second dose. The antibody laboratory title cut-off of 50 U.A./mL defined the seroconversion. Results are shown as Mean and Standard Deviation for Scontinuous variable, percentage (%) for categorical ones. The Mann-Whitney test or Chi-Square test were used to compare continuous or categorical groups, respectively. Results: A total of 100 patients with breast cancer were enrolled. Clinical and demographic data are summarized in Table 1. The median age was 60.5 years and the majority had an ECOG PS of 0 (75%). Almost all were women (97%), with advanced cancer in 60% of cases. In early or advanced setting 46% patients were treated with chemotherapy while 54% were on target therapy (also including monoclonal antibody and CDK4/6 inhibitors). The mean antibody title after the first dose of mRNA Comirnaty vaccine was 2185.03±9303.26 U.A./mL (M±SD), while after the second dose the mean antibody title rise to 6492.10±10425.95 (M±SD). After the first dose 61% of patients were considered as immunized, meanwhile after the second dose 86% of patients resulted immunized (defined as an antibody title >50 U.A./mL). In the 9 patients in treatment with steroids (prednisone > 10mg/die or equivalent), there was a trend to a decreased antibody development compared to patients without chronic use of steroids (p 0.06 and 0.05 after the first and second dose, respectively). Of interest, patients using G-CSF (12%) had a significant reduction in the production of Sars-Cov2 antibody after vaccination compared to patients who did not use them (p 0.02 and <0.001 after the first and second dose, respectively), with only 75% resulted positively immunized after the second dose (p=0.04). No differences were seen when comparing patients in advanced with non-advanced stage. Conclusions: Our study demonstrated 86% seroconversion in cancer patients after the second dose of mRNA vaccine regardless of disease stage or type of cancer treatment received. Further evaluations are needed to define whether the use of corticosteroids and G-CSF have an impact on seroconversion.