Humoral Immune Response of SARS‐CoV‐2–Infected Patients with Cancer: Influencing Factors and Mechanisms

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2)–infected patients with cancer show worse outcomes compared with patients without cancer. The humoral immune response (HIR) of patients with cancer against SARS‐CoV‐2 is not well characterized. To better understand it, we conducted a serological study of hospitalized patients with cancer infected with SARS‐CoV‐2. MATERIALS AND METHODS: This was a unicentric, retrospective study enrolling adult patients with SARS‐CoV‐2 admitted to a central hospital from March 15 to June 17, 2020, whose serum samples were quantified for anti–SARS‐CoV‐2 receptor‐binding domain or spike protein IgM, IgG, and IgA antibodies. The aims of the study were to assess the HIR to SARS‐CoV‐2; correlate it with different cancer types, stages, and treatments; clarify the interplay between the HIR and clinical outcomes of patients with cancer; and compare the HIR of SARS‐CoV‐2–infected patients with and without cancer. RESULTS: We included 72 SARS‐CoV‐2–positive subjects (19 with cancer, 53 controls). About 90% of controls revealed a robust serological response. Among patients with cancer, a strong response was verified in 57.9%, with 42.1% showing a persistently weak response. Treatment with chemotherapy within 14 days before positivity was the only factor statistically shown to be associated with persistently weak serological responses among patients with cancer. No significant differences in outcomes were observed between patients with strong and weak responses. All IgG, IgM, IgA, and total Ig antibody titers were significantly lower in patients with cancer compared with those without. CONCLUSION: A significant portion of patients with cancer develop a proper HIR. Recent chemotherapy treatment may be associated with weak serological responses among patients with cancer. Patients with cancer have a weaker SARS‐CoV‐2 antibody response compared with those without cancer. IMPLICATIONS FOR PRACTICE: These results place the spotlight on patients with cancer, particularly those actively treated with chemotherapy. These patients may potentially be more vulnerable to severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection, so it is important to provide oncologists further theoretical support (with concrete examples and respective mechanistic correlations) for the decision of starting, maintaining, or stopping antineoplastic treatments (particularly chemotherapy) not only on noninfected but also on infected patients with cancer in accordance with cancer type, stage and prognosis, treatment agents, treatment setting, and SARS‐CoV‐2 infection risks.