1676MO Prevalence and clinical impact of asymptomatic or mildly symptomatic SARSCoV-2 infection among actively treated cancer patients during COVID-19 pandemic in Italy

Background: The European SARS-CoV-2 pandemic had its first epicentre in Italy, particularly in the area of Bergamo In spite of a significant mortality rate, in the majority of cases the spectrum of COVID-19 ranges from asymptomatic to mildly symptomatic infection No information is available on the prevalence and clinical impact of asymptomatic or mildly symptomatic SARS-CoV-2 infection among actively treated cancer patients during pandemic Methods: From April 1st, 2020 to the end of the month, 560 consecutive and unselected patients, scheduled for anticancer treatment at our facility and without clinical suspicious of COVID-19, were evaluated and tested for SARS-CoV-2 We implemented a two-step diagnostics, including a rapid serological immunoassay for anti-SARS-CoV-2 IgG/IgM and a pharyngeal swab RT-PCR assay in case of IgM seropositivity Results: In 560 patients, 172 (31%) resulted positive for SARS-CoV-2 IgM/IgG antibodies, regardless of type of cancer, stage and treatment All IgM-seropositives were then tested with RT-PCR pharyngeal swabs and 55/146 (38%) proved to be SARS-CoV-2 carriers, with slightly difference b/w mildly symptomatic vs asymptomatic patients (38 vs 17) Therefore, the two-step procedure allowed the identification of 55 (10%) silent carriers in the whole study population and magnified the number needed to test (NNT) with the pharyngeal swab RT-PCR assay to detect a silent virus carrier (NNT: 2 6 vs 10, with or without serological selection) At a very early follow up (8 wks), in 114 SARS-CoV-2-seropostive/RT-PCR-negative patients, who continued their anticancer therapies, none but one developed a symptomatic COVID-19 illness Conclusions: Among cancer patients, the two-step diagnostics strategy with serology followed by pharyngeal swab for asymptomatic or mildly symptomatic SARS-CoV-2 infection is feasible and effective and can help selecting cancer patients on treatment who might be silent carriers of the virus The early safety outcome of patients previously exposed to SARS-CoV-2 supports the recommendation to continue active treatment, at least in the case of negative RT-PCR test Legal entity responsible for the study: The authors Funding: Has not received any funding Disclosure: All authors have declared no conflicts of interest