e23093 Background: Despite vaccination, COVID-19 could still cause severe disease in immunocompromised patients (pts). While subsequent vaccine doses increase immune response in the general population, few data concerning cancer pts under systemic treatment are reported. Methods: This study will be conducted on blood samples from 1000 pts admitted to Reggio Emilia AUSL-IRCCS Cancer Center and undergoing systemic therapies who received ≥ 2 vaccine doses. The samples will be analyzed at Clinical Microbiology and Chemistry Laboratories of Reggio Emilia AUSL-IRCCS. We will perform antibody IgM-IgG serology by means of COVID-19 VIRCLIA® Monotest and anti-spike antibodies evaluation using LIAISON® SARS CoV-2 Trimerics IgG. We will also investigate cell immune response (B and T lymphocyte counts) and analyze specific lymphocyte subsets on the first 200 pts treated with chemo- (CT) or immunotherapy (IO). Then, we will evaluate the T-cell response on the first 50 pts and those with an inadequate anti-spike serologic response through the T-SPOT.COVID test. Statistical analyses will be conducted by the Clinical Studies and Statistical Unit Staff. Results: Here, we report preliminary data on the first 240 pts enrolled and treated with CT (55.4%), IO (26.3%), or other therapies (18.3%). Most of the pts were male (58%), had metastatic cancer (82%), and no previous COVID-19 infection (60%). 84% of pts were affected by gastrointestinal, lung, urogenital and breast cancer. We stratified pts in three groups according to the time from the last vaccine dose (0-6/6-12/ > 12 months). We showed no significant decrease in cellular and humoral immune response over time from the last vaccine dose, independent of the specific treatment received, also if CT (Table 1). Furthermore, clinical characteristics as gender, treatment, and primary tumor site appear not to influence immune response, even if a trend to a higher response in pts previously affected by COVID-19 has been observed. The T-SPOT.COVID test performed on the first 27 pts showed that 19% had no T-cell activation, even with good IgG response. Conclusions: This feasible and cost-effective study has a potential impact on public health. Although these are preliminary data, the immune response to COVID-19 vaccines remains good after 12 months from the last dose administered in cancer pts. The enrollment is ongoing, and we could provide relevant information on the influence of clinical factors on the immune response and identify specific subgroups that could benefit from different vaccine approaches. [Table: see text]

Introduction: More than 2 years after the WHO declaration of a pandemic, SARS-Cov-2 still represents a public health problem The pandemic has increased the complexity of cancer treatments including breast cancer. These difficulties were highlighted in adjuvant treatments but above all in metastatic disease. Vaccination has been one of the most important public health factors that has reduced deaths, hospitalizations and the severity of symptoms related to infection. In metastatic breast cancer hormone receptor positive and HER2/neu negative currently the first line of treatment is given by the association between cyclin 4/6 inhibitors and hormone therapy (aromatase inhibitors or fulvestrant) A well-known and frequent side effect of this therapy is the reduction of white blood cell values and neutrophils. The hypothesis that this study is to evaluate whether treatment with cyclin inhibitors initiated before the period of vaccinations may have influenced, due to the reduction in white blood cell values, an increased risk of infection in these patients. Materials and methods: In our study, we selected patients who had started treatment with cyclin inhibitors before starting the vaccination cycle (in Italy up to the fourth dose in cancer patients) and continue it without evidence of disease progression. All patients were offered a vaccination cycle with mRNA COVID vaccines and were followed during their cancer treatments. All patients, at least 90 days after the last dose of vaccine, have been tested for antibodies against SARS CoV-2 (trimeric spike protein) with a value expressed in binding antibodies unit (BAU) according to international standard WHO During the observation period (starting from the first dose of vaccine administered) the patients were clinically checked and in case of suspicion of infectious pathology with symptoms suggestive of SARS-COV-19 infection, they were tested with molecular swab Results: We evaluated 52 patients who started cyclin treatment before the vaccination course and who are currently without signs of disease recurrence During the study period we found 14 SARS-COV19 infections (28% of patients) and one patient with two infectious episodes. No patients needed treatment in a hospital or resuscitation setting. All patients have fully recovered from the infection and at most after 21 days have resumed the treatment still in place Statistically, a linear regression calculation was applied to evaluate a functional relationship between variables measured on the basis of sample data. We did not find a relationship between spikes or infections compared to the start date of the vaccination cycle; instead we observed a relationship between the value of the spike and the date of last immunization (considered as an active infection or fourth dose of vaccine) with a reduction in the values the further you go away Conclusion: The data of the study show that there is a correlation between the time elapsed between the last vaccination and the risk of getting sick. For this reason, the fourth recall represents a strong help to reduce this risk. We did not find any ranges we could refer to regarding the dosage of trimeric spike protein. Considering the positivity rate of infections that does not exceed the general vaccinated population and the absence of serious infectious symptoms with hospitalization, treatment with cyclin inhibitors appears to be a safe treatment even in a pandemic period. Last day immunization and spike with IA or fulvestrant Last day immunization and spike with IA or fulvestrant Citation Format: Filippo Giovanardi, Edoardo Carretto, Giancarlo Bisagni, Claudia Degli Esposti, Elisa Gasparini, Alessandra Bologna, Roberto Di Cicilia, Gabriella Moretti, Carmine Pinto. Cyclin-dependent kinase 4/6 inhibitor in advanced breast cancer during the COVID pandemic period: efficacy in relation to vaccination for SARS-COV 19 [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-03-04.