New study links cystitis to higher risk of urogenital cancers

A bout of the common bladder infection, cystitis, may signal the presence of urogenital cancers-which affect parts of the body involved in reproduction and excretion-in middle aged adults, suggests research published in the open access journal BMJ Public Health. 

The risks seem to be especially high within 3 months of infection, suggesting that acute cystitis might be a useful clinical marker for urogenital cancer, say the researchers. Men seem to be at greater risk than women, the findings indicate.

The lifetime prevalence of a urinary tract infection (UTI) is 50–60% in women and 13–14% in men. With the exception of a spike in young women, incidence rates of UTIs increase with age in both men and women, note the researchers.

Previously published research has shown that a bout of cystitis might be linked to an increased risk of urogenital cancers, but only a few such studies have been published and they didn’t include data from primary care facilities, which is where most cases of acute cystitis are diagnosed, they explain.

To try and plug this knowledge gap, the researchers mined several comprehensive national population and health registers and primary healthcare data sources, containing individual-level information on all people living in Sweden from 1997 to the end of 2018.

Data were available for 1,668,371 (47%) men and 1,889,211 (53%) women during this period, of whom 605,557 (17%) people were diagnosed with acute cystitis for the first time. 

Most of these diagnoses (91%) were made in primary care facilities and most cases were in women (71%; 427,821). 

During an average monitoring period of 15 years, a total of 257,026 (just over 7%) people were diagnosed with urogenital cancer, most of whom were men (77.5%; 199,144).

The average age at cancer diagnosis was 73, with prostate cancer the most common cancer type (62%), followed by bladder cancer (16.5%), and endometrial (lining of the womb) cancer (10%).

Cystitis preceded a cancer diagnosis in 24,137 people–almost 9.5% of all those diagnosed with cancer during the study period. Their average age at diagnosis was 76: prostate cancer was the most common diagnosis (39.5%), followed by bladder (32%), and endometrial (14%) cancer. 

The risks of a urogenital cancer diagnosis were heightened across all age groups among those who had had a bout of cystitis, and peaked within 3 months of infection, especially for prostate and bladder cancers, but persisted over several years for most cancers. 

For prostate cancer, the risk, measured as a standardized incidence ratio (SIR) within 3 months of infection was 7 times higher in those who had had the infection than it was in those who hadn’t. 

This corresponds to an excess cancer rate of nearly 551 per 10, 000 person-years–a unit of measurement that combines the number of people and the time during which they were observed. For example, 10,000 patients monitored for 1 year or 1000 patients monitored for 10 years.

Similarly, the risk of bladder cancer was 3.5 times higher in men and more than 3 times higher in women who had had cystitis than it was in those who didn’t have the infection during the monitoring period. This corresponds to an excess rate of around 40 and nearly 8 more cancer cases, respectively, than would be expected per /10,000 person-years.

For gynecologic cancers, the SIRs within 3 months of infection were between 4 and 8 times higher among women who had had cystitis. 

Overall, the risk of urogenital cancer was nearly 34 times higher in men and 30 times higher in women, within 3 months of infection, corresponding to nearly 484 and 96 excess cancer rates/10,000 person-years, respectively.

While the risks fell as time went on, they persisted throughout all the follow-up periods for both sexes. For example, 3–12 months after infection, the excess cancer rates/10,000 person-years were more than 79 in men and more than 19 in women. And after 5 years, these were around 9 in men and 2.5 in women.

In general, men who had had cystitis seemed to be at higher risk of urogenital cancer than women: for example, their risk of bladder cancer was twice as high for those in their 50s, 57% higher for those in their 60s, and 23% higher for those in their 70s.

This is an observational study, and as such, no firm conclusions can be drawn about cause and effect. And the researchers acknowledge that they lacked microbiological confirmation of cystitis infection or information on potentially influential factors, such smoking and underlying conditions, including obesity and undiagnosed diabetes.

But they say: “The present study adds to the accumulating evidence of infections as markers of increased cancer risk. For clinicians, the findings indicate that acute cystitis could be a clinical marker for urogenital cancer (at least when no other cause is obvious), and particularly for occult urogenital cancer, as the risks for cancers were highest within 3 months of cystitis diagnosis.” 

They add: “It is plausible that urogenital cancer, and perhaps even pre-cancerous changes in the urogenital organs, might increase the risk of cystitis because of compromised urinary tract and host defence.”