Acute cystitis and subsequent risk of urogenital cancer: a national cohort study from Sweden.

Introduction: This study aimed to examine the subsequent risks of urogenital cancers in men and women aged ≥50 years diagnosed with acute cystitis. Methods: A Swedish nationwide cohort study was conducted that included primary healthcare data. The total population consisted of 1 668 371 men and 1 889 211 women; of these, 177 736 men and 427 821 women were diagnosed with acute cystitis (first event) during 1997-2018 (91.3% in primary healthcare settings). The outcome was urogenital cancer in men and women with cystitis compared with the total population, measured as standardised incidence ratios (SIRs) and excess rates per 10 000 person-years. Results: A total of 199 144 men and 57 882 women were diagnosed with urogenital cancer (24 137 subsequently to cystitis). The most common cancers were prostate and bladder cancer. The urogenital cancer risks were elevated across all age groups of men and women with cystitis. The risks were highest within 3 months of follow-up but persisted over several years for most cancers. The risks within 3 months of follow-up were as follows: for bladder cancer, the SIR was 33.69 (95% CI 32.02 to 35.43) in men and 30.00 (28.02 to 32.09) in women, corresponding to 483.72 and 96.00 excess cancer rates per 10 000 person-years, respectively. For prostate cancer, the SIR was 7.05 (6.74 to 7.37) and the excess cancer rate was 550.88 per 10 000 person-years; between 3 and 12 months of follow-up, the excess rate was 104.89 per 10 000 person-years. For kidney cancer, the SIR was 11.28 for men and 7.72 for women. For gynaecological cancers, SIRs were between 4 and 8. Some interactions were observed between sex and cystitis in relation to urogenital cancer risks. Conclusion: Acute cystitis can precede urogenital cancers in men and women aged ≥50 years. The increased risks were particularly high within 3 months after the acute cystitis event and persisted for several years.