BACKGROUND AND OBJECTIVES: Underlying occult cancer could potentially explain some of the observed increased long-term mortality among patients with brain abscess.
METHODS: Nationwide, population-based health care registries were used to examine long-term risks of cancer in patients with brain abscess from 1982 to 2016 compared with a population comparison cohort individually matched (10:1) on age, sex, and residence. Cumulative incidences and adjusted cause-specific hazard rate ratios (HRRs) with 95% CIs for cancer were computed. Potential confounding by family-related factors was explored by comparing cumulative incidences of cancer among siblings of both groups.
RESULTS: Among 1,384 patients with brain abscess (37% female, median age 50 years, interquartile ranges [IQR] 33-63), cancer was observed in 218 (16%) compared with 1,657 of 13,838 (12%) in the comparison cohort yielding an adj. HRR of 2.09 (95% CI 1.79-2.45). The median time to diagnosis of cancer was 1.8 years (IQR 0.02-9.1) in patients with brain abscess and 8.6 years (IQR 3.9-15.9) in comparison cohort. Among patients with brain abscess, CNS and eye cancer was diagnosed in 59 (4.3%), of which 47 of 59 (80%) occurred within 90 days of the admission date, metastasizing cancer in 54 (3.9%), respiratory tract cancer in 48 (3.5%), and gastrointestinal cancer in 36 (2.6%). Results remained consistent in almost all subgroups and in sensitivity analyses. Accounting for competing risk of death, the 1-, 5-, 10-, and 35-year cumulative incidence of cancer was 7% (95% CI 6-8), 11% (95% CI 9-12), 13% (95% CI 11-15), and 24% (95% CI 20-27) in patients with brain abscess compared with 0.7% (95% CI 0.6-0.9), 4% (95% CI 4-5), 8% (95% CI 8-9), and 25% (95% CI 23-27) in the comparison cohort, respectively. The cumulative incidences of cancer among siblings of patients with brain abscess were 10% and 12% among siblings of the comparison cohort.
DISCUSSION: Brain abscess was associated with substantially increased risk of cancer during the first 10 years after diagnosis.