Prevalence and Clinical Impact of SARS-CoV-2 Silent Carriers Among Actively Treated Patients with Cancer During the COVID-19 Pandemic.

Introduction In Europe, the SARS-CoV-2 pandemic had its first epicenter in Italy, particularly in the area of Bergamo. Despite a significant mortality rate, the severity of most cases of COVID-19 infection ranges from asymptomatic to mildly symptomatic, and silent infection affects a still unknown proportion of the general population. No information is available on the prevalence and clinical impact of SARS-CoV-2 silent infection among cancer patients receiving anticancer treatment during the pandemic. Patients and methods From the April 1, 2020, to the end of the same month, 560 consecutive cancer patients, asymptomatic for COVID-19 and on anticancer treatment at Papa Giovanni XXIII Hospital in Bergamo, were evaluated and tested for SARS-CoV-2. We implemented a two-step diagnostics, including the rapid serological immunoassay for anti-SARS-CoV-2 IgG/IgM and the nasopharyngeal swab RT-PCR [reverse transcriptase-polymerase chain reaction] test in case of seropositivity to identify SARS-CoV-2 silent carriers. Results In 560 patients, 172 (31%) resulted positive for anti-SARS-CoV-2 IgM/IgG antibodies, regardless of different type of cancer, stage, and anticancer treatment. The Ig-seropositive patients were then tested with RT-PCR nasopharyngeal swabs, and 38% proved to be SARS-CoV-2 silent carriers. Testing only in case of seropositivity magnified the SARS-CoV-2 silent carriers detection and predicted an RT-PCR number-needed-to-test calculation of 2.5, versus 10 for testing the whole population with RT-PCR. At an early follow-up, in the 97 SARS-CoV-2-seropostive/RT-PCR-negative patients who continued their anticancer therapies, only one developed symptomatic COVID-19 illness. Conclusion Among cancer patients, the two-step diagnostics is feasible and effective for SARS-CoV-2 silent carriers detection and might support optimal cancer treatment strategies at both the individual and the population level. The early safety profile of the different anticancer therapies, in patients previously exposed to SARS-CoV-2, supports the recommendation to continue the active treatment, at least in cases of RT-PCR-negative patients. Implications for practice This is the first study evaluating the prevalence and clinical impact of SARS-CoV-2 silent infection in actively treated cancer patients, during the epidemic peak in one of the worst areas of the Covid-19 pandemic. Lacking national/international recommendations for the detection of asymptomatic SARSCoV-2 infection, a pragmatic and effective two-step diagnostics was implemented to ascertain SARSCoV-2 silent carriers. In our series, consisting of consecutive and unselected cancer patients, the prevalence of both SARSCov-2 seropositive patients and silent carriers is substantial (31% and 10%, respectively) The early safety profile of the different anticancer therapies, in patients previously exposed to SARSCoV-2, supports the recommendation to continue the active treatment, at least in case of RT-PCR negative patients.