Increased risk of incident primary cancer after Staphylococcus aureus bacteremia: A matched cohort study

Susceptibility to infectious disease may be a marker of immunodeficiency caused by unrecognized cancer. To test the hypothesis, the risk of incident primary cancer was estimated among survivors of Staphylococcus aureus bacteremia (SAB) and compared to a random population cohort. Nation-wide population-based matched cohort study. Cases of SAB were identified from a national database and incident primary cancers were ascertained by record linkage. Incidence rate (IR) and ratio (IRR) with 95% confidence interval (CI) of 27 cancers was calculated by Poisson regression. During the first year of follow-up, 165 and 943 incident cases of cancer occurred in the case cohort (n = 12,918 (1.3%)) and the population cohort (n = 117,465 (0.8%)) for an IR of 3.78 (3.22–4.40) and 2.28 (2.14–2.43) per 100,000 person-years. The IRR was 1.65 (1.40–1.95). Of 27 cancers, 7 cancers occurred more frequently amongst cases than controls: cervical cancer (IRR 37.83 (4.23–338.47)), multiple myeloma (IRR 6.31 (2.58–15.44)), leukemia (IRR 4.73 (2.21–10.10)), sarcoma (IRR 4.73 (1.18–18.91)), liver cancer (IRR 3.64 (1.30–10.21)), pancreatic cancer (IRR 2.8 (1.27–6.16)), and urinary tract cancer (IRR 2.58 (1.23–5.39)). Compared to the control population, the risk of cancer was higher for those without comorbidity and with younger age. The overall risk of cancer during 2 to 5 years of follow-up was not increased (IRR 0.99 (95% CI: 0.89–1.11). However, the risk of pharyngeal cancer was increased (IRR 1.88 (1.04–3.39)) and the risk of liver cancer remained increased (IRR 3.93 (2.36–6.55)). The risk of primary incident cancer was 65% higher in the SAB cohort compared to the population cohort during the first year of follow-up and included 7 specific cancers. The risk was higher for those without comorbidity and with younger age. Screening for these specific cancers in selected populations may allow for earlier detection.