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Workplace factors influence bladder cancer incidence, mortality risks
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Exposure to certain occupational carcinogens appeared associated with increased bladder cancer incidence and mortality rates, according to the results of a systematic review and meta-analysis.
Researchers also observed an increase in bladder cancer incidence, especially among women.
“Bladder cancer is the fourth commonest male malignant neoplasm worldwide,” James W.F. Catto, MBChB, PhD, FRCS, professor of urological surgery at University of Sheffield in England, and colleagues wrote. “The two most frequent routes of exposure are through tobacco smoking and occupation. … In 1981, Doll and Peto estimated that 10% of bladder cancers arose from occupational exposure. Given the 20- to 30-year latency between exposure and cancer, we expected that workplace legislation has now reduced that rate.”
Catto and colleagues sought to determine the current risk profiles for occupational bladder cancer. They used PubMed, Medline, Embase and Web of Science to perform a systematic review for articles related to the subject.
The researchers initially identified 263 eligible articles. They excluded articles in which bladder cancer or occupation did not serve as the main focus, as well as those with insufficient case, risk or CI data.
The evaluation of the current risk profile for occupational bladder cancer and the change in risk over time served as the primary endpoints.
Overall, researchers observed increased bladder cancer incidence in 42 of 61 occupational classes, as well as increased bladder cancer-specific mortality in 16 of 40 occupational classes.
Conversely, reduced incidence occurred in six of 61 cases and reduced mortality occurred in two of 40 cases.
The highest individual reported incidence risks occurred among factory workers (RR = 16.6; 95% CI, 2.1-131.3), hairdressers (RR = 13.4; 95% CI, 1.5-48.2) and aircraft or ship’s officers (RR = 11.8; 95% CI, 1.5-95.7). The highest reported mortality rates occurred among chemical (RR = 27.1; 95% CI, 11.7-53.4) and dye workers (RR = 8.3; 95% CI, 1.7-24.8).
Workers in these industries tended to be exposed to heavy metals and polycystic aromatic hydrocarbons, diesel and combustion products, and aromatic amines.
Agricultural workers appeared to be at the lowest risk for bladder cancer.
Further, the researchers found that risk varied by sex, with men exhibiting the greatest risk (standard incidence ratio [SIR] = 1.03; 95% CI, 1.02-1.03).
Between the 1960s and the 1980s, a steady decline in SIR occurred for both sexes; however, the trend reversed in the 1980s. In the decade 2000 to 2010, the SIR increased to 1.13 for men (95% CI, 1.07-1.19) and 1.27 for women (95% CI, 1.12-1.43).
However, bladder cancer mortality risk declined for both sexes from the 1960s to the 1990s, with men at greater overall risk for bladder cancer mortality than women (men: standard mortality ratio [SMR] = 1.32; 95% CI, 1.18-1.48; women: SMR = 1.14; 95% CI, 0.8-1.63).
The researchers identified limitations of their study, including potential publication bias, as well as the use of job title to stratify workers rather than task. Further, they noted that not all studies adjusted for smoking and that the majority of studies included were conducted in Western countries only.
“While there have been reductions in occupational bladder cancer incidence and mortality, it appears that there may still be many occupations with an elevated incidence or mortality risk,” Catto and colleagues wrote. “This persists despite improvements in workplace hygiene, although the profile of at-risk occupations has changed over time and may differ for bladder cancer incidence and mortality. … Recent data suggest that the risk [for] occupational bladder cancer is rising and effecting women more than men. This may be due to an increase in the number of women in the workforce or the emergence of occult carcinogens in occupations predominated by women.”
Despite improvements in workplace safety, further improvements could influence future incidence and mortality risks for bladder cancer, Elisabete Weiderpass, MD, MSc, PhD, of the Institute of Population-Based Cancer Research in Oslo, Norway, and Harri Vainio, MD, PhD, of the Finnish Institute of Occupational Health in Helsinki, wrote in an accompanying editorial.
“Bladder cancer can be prevented by avoiding its causes,” Weiderpass and Vainio wrote. “This has been demonstrated through the identification of the carcinogenicity of beta-naphthylamine in work processes — particularly in the dye industry — followed by a reduction and substitution with supposedly reduction on the occurrence of bladder cancer thereafter. But, like Alice in Wonderland, epidemiologists and occupational health specialists may feel that each discovery leads to a ‘curiouser and curiouser’ set of further questions. … Bladder cancer continues to vary considerably by occupation, sex and calendar time — all indications that prevention is possible and warranted. Workers around the world have the right to demand and get a safe and carcinogen-free workplace.” – by Cameron Kelsall
Disclosure: The researchers report no relevant financial disclosures. Weiderpass and Vainio report no relevant financial disclosures.
Perspective
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Alexander Kutikov, MD, FACS
This work is arguably the most comprehensive assessment to date of the link between occupational carcinogen exposure and urothelial carcinoma of the bladder. Meta-analysis of peer-reviewed literature revealed that workers in certain professions are more likely than others to develop and succumb to bladder cancer. Although incidence was highest for workers in the tobacco industry, metal workers exhibited approximately a tenfold higher-than-baseline risk for dying from bladder cancer. Exposure to aromatic amines was associated with increased incidence of bladder cancer, whereas polycyclic aromatic hydrocarbon contact was linked with the highest mortality rates. Meaningful comparisons across time periods within occupational groups were challenging; however, authors do describe a notable trend toward lower bladder cancer rates amongst drivers.
These data not only afford actionable targets for occupational exposure reductions, but also identify high-risk populations who are most likely to benefit from urothelial carcinoma screening as new biomarkers for bladder cancer become available.
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