SER-ONCOVID: Seroconversion in solid-tumor cancer patients after COVID-19 diagnosis.

2544 Background: Cancer patients (pts) represent a high-risk population for severe COVID-19. Cancer-associated immunosuppression may hinder in the development of anti-SARS-CoV-2 antibodies. Methods: Data regarding baseline characteristics, COVID-19 and anti-SARS-Cov2 IgG were collected from cancer pts (solid tumors) who tested positive for COVID-19 (PCR+) between March and April 2020 at Catalan Institute of Oncology. We prospectively assessed anti-SARS-Cov2 IgG seroprevalence at 3 and 9 months post infection and explored clinico-pathologic factors associated with IgG positivity. We explored the impact of potential factors influencing antibody production at >9 months. Results: Of 49 pts registered between 10th March-26th April 2020, 21 died <3 months after the infection and 5 pts refused to participate, leaving 23 eligible pts for IgG testing. With respect to those not tested, IgG tested cohort was younger (median age: 64.0 vs 72.9 years, p = 0.001) and presented oncologic remission in 68.2% of cases (vs 34.6%, p = 0.043) at COVID-19 diagnosis. Median time from PCR+ to first and second IgG determination was 3.2 months (Interquartile range [IQR]: 2.9-4.1) and 9.5 months (IQR: 8.8-9.8), respectively. Out of 23 pts, 15 had both determinations and 8 had only one (3 in the first time point, 5 in the second one). We identified 16/18 pts IgG+ (88.9%) at 3 months and 17/20 pts IgG+ (85%) at 9 months. One IgG+ pt became IgG- at the second determination, one was IgG- at both timepoints, and one had an inconclusive result at the first but negative at the second timepoint. Key characteristics of patients by IgG result 9 months after COVID-19 diagnosis are shown in the table. Conclusions: We describe a high seroprevalence of anti-SARS-CoV-2 IgG at 3 and 9 months after COVID-19 diagnosis in solid tumour patients, irrespective of anti-cancer therapy exposure. Pts who were IgG+ at 9 months were older, and more likely to have required oxygen during prior COVID-19 in comparison to IgG- pts suggesting that infection severity may promote durable immunity. Frequency of early stage cancers was higher among IgG+ pts, suggesting less cancer-related immunosupression. Older (>70 years) and advanced cancer pts were under-represented in this series, warranting confirmation of these preliminary results in a larger cohort.[Table: see text]