BACKGROUND: Patients with history of active malignancy are at increased risk of infection and COVID-19 related complications . Sanitary protection measures are not specifically recommended within household . We wanted to study the risk of seroconversion in cancer patients according to their household exposure . PATIENTS AND

METHODS: The seroprevalence study is a prevalence study in Torrejon de Ardoz (Spain), and analyzed the seeroprevalence of IgM and IgG antibodies in 104,299 volunteers (participation rate of 74.8% of population) from May 29th to June 5th , 2020 . Personal authorization was requested to collect by questionnaire the test result from cancer patients who attended the outpatients department of the University Hospital of Torrejón and their cohabitants between June 1 st and June 19th 2020 .

RESULTS: 229 cancer patients were included in the study . Sixty-four of the 229 individuals tested positive for SARS-CoV-2 IgG antibodies (27.9 %) and 22 patients were positive for SARS-CoV-2 IgM antibodies (9.6 %). The overall seroprevalence (IgG or IgM positive) was 31.4% (general population seroprevalence was of 10% in Spain). Of 72 seropositive patients, 54.2% had intrafamilial exposure vs 45.8% did not . Among seronegative patients , 30.6% had seropositive cohabitants . The probability of seropositivity for a cancer patient was significantly related to intrafamilial exposure (OR of 2.684 , 95% CI 1.51 - 4.76, p = 0.001).

CONCLUSIONS: Cancer patients are a high-risk group for SARS-CoV-2 infection, and could need to implement recommendations against virus transmission even in a household scenario as it is the main factor significantly related to seroconversion.