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.