Risk of severe COVID-19 outcomes in individuals with prior cancer diagnosis – A nationwide Swedish register-based cohort study

BACKGROUND: Individuals with cancer are recognized as a high-risk group for severe COVID-19, yet population-based evidence across cancer types remains limited. This study assessed associations between previous cancer diagnoses and COVID-19 outcomes among individuals diagnosed with different cancers. METHODS: We included the entire Swedish population on 1 Jan 2020 (n = 10,390,479). Cancer diagnoses from 2015 to 2019 were identified from the Swedish National Cancer Register. COVID-19 outcomes (infection, hospitalization, intensive care, and death) from 1 Jan 2020-31 Dec 2021 were retrieved from national registers. Cox regression estimated hazard ratios (HR) with 95% confidence intervals (CI), controlling for age, sex, comorbidity and sociodemographic factors. RESULTS: We identified 234,582 individuals with cancer diagnosis, among whom 20,329 had COVID-19 infection, 5010 were hospitalized, 423 admitted to intensive care, and 1664 died. Compared with individuals without recent cancer (N = 10,155,897), those with cancer had a slightly lower HR of COVID-19 infection (0.97, 95% CI 0.96-0.99) but higher HRs of hospitalization (1.18, 1.14-1.21) and death (1.18, 1.13-1.25). Those with respiratory cancer had the highest HR for hospitalization (1.51, 1.36-1.68) and death (2.35, 1.98-2.79), and those with breast or prostate cancer showed lower HR for COVID-19 infection (0.95, 0.92-0.98 and 0.83, 0.80-0.86). Only prostate cancer was associated with a slightly lower, non-significant, risk of COVID-19-related death (0.92, 0.81-1.04). CONCLUSIONS: Overall, a previous cancer diagnosis was associated with a slightly lower hazard of recorded COVID-19 infection. The risk of severe COVID-19 outcomes differed across cancer types. Our results highlight heterogeneity in COVID-19 outcomes across types. These findings support consideration of cancer type when assessing vulnerability during public health crisis.