Chapter 4: Cancer incidence in Canada: trends and projections (1983-2032) – Bladder cancer - HPCDP: Volume 35, Supplement 1, Spring 2015

Chapter 4: Projections by Cancer Site

17. Bladder cancer

Bladder cancer is the only site where we combine in situ and malignant cases. The provincial and territorial cancer registries, other than Ontario, have combined in situ and invasive bladder cancers when reporting to the Canadian Cancer Registry (CCR). Reasons for the reporting include the difficulty in identifying early invasion in pathology reports and the high rates of recurrence and progression of in situ tumours.^{Endnote 241, Endnote 242, Endnote 243}

Bladder cancer was the fourth most common type of new cancer diagnosis in Canadian males and the eleventh most common type in Canadian females in 2003–2007. One in 28 males and 1 in 78 females can expect to be diagnosed with bladder cancer in their lifetime, and 1 in 89 males and 1 in 213 females can expect to die from it.^{Endnote 1} The average annual number of new bladder cancer cases in 2003–2007 was 4815 for males and 1705 for females, constituting 6.0% and 2.3% of all male and female cancer cases, respectively (Table 4.17.1 and 4.17.2).

The incidence increased exponentially with age for males and linearly for females in the last observation period (2003–2007) (Tables 4.17.3 and 4.17.4).

As such, the male-to-female ratio of the rates increased with age, from 2.0:1 in young adults (<45) to 3.9:1 in the oldest (85+) (Figure 4.17.2). About 71% of all bladder cancers were diagnosed in people aged 65 or older in the same period. The 5-year relative survival rate was 74% for bladder cancer diagnosed between 2006 and 2008.^{Endnote 1}

For males, the ASIRs in all regions were relatively stable between 1988 and 2002 but displayed a downward trend in the last 10 years (Figure 4.17.1). For females, the rates in all regions remained stable. However, in the last observed decade, the rates in females increased moderately in Quebec and the Atlantic region and decreased markedly in British Columbia. During 1998–2007, bladder cancer ASIRs decreased significantly in males by 0.7% per year, and the ASIRs in females were stable, with a non-significant decrease of only 0.1% per year (Figures 3.1 and 3.2).

The rates for males are anticipated to decrease, but at different levels, in all regions (Figure 4.17.1). Female rates are projected to increase slightly in Quebec, and stabilize in the other areas. Internal ranking of the ASIRs in geographical regions is predicted to be similar for both sexes, with the highest rates in Quebec and the lowest in British Columbia. From 2003–2007 to 2028–2032, the ASIRs of bladder cancer for Canada are projected to decrease by 14% in males, from 27.9 to 24.0 per 100 000, and to drop by 6% in females, from 7.7 to 7.3 per 100 000 (Tables 4.17.3 and 4.17.4). With the aging and growth of the population, however, the annual number of new cases in males will increase by 83%, from 4815 to 8825, and in females by 78%, from 1705 to 3030 (Tables 4.17.1 and 4.17.2).

Allowing for the expected number of Ontario in situ cases, the increase for Canada as a whole from 2003–2007 to 2028–2032 would be from approximately 5510 to 10 135 cases annually in males and from 2005 to 3560 cases in females. The annual number of new Ontario cases adjusted for in situ cases would rise over this period from about 2045 to 3825 in males and from 785 to 1385 in females. The corresponding prediction for the adjusted Ontario ASIRs would be a decrease from 31.1 to 26.4 per 100 000 in males and a decrease from 9.4 to 8.8 per 100 000 in females.

Comments

For the data used in this monograph, Ontario has not reported in situ bladder cancer, resulting in the lower bladder cancer rates observed for Ontario. Ontario will start including these cases in future data releases. Based on data collected for 2000–2002 (but not included in the Ontario Registry), ^{Endnote 1} it is expected that this reporting change in Ontario will result in observed bladder cancer rates close to those of the Prairie region and British Columbia, representing an increase in Ontario cases of 52% in males and 62% in females with a similar increase in rates.

Cigarette smoking is the major and preventable risk factor for bladder cancer.^{Endnote 47, Endnote 86} Smoking accounted for about 50% of male bladder cancer cases and 30% of female bladder cancer cases in Europe.^{Endnote 244, Endnote 245} Current smokers have up to 4-fold higher risk of bladder cancer than non-smokers, ^{Endnote 246, Endnote 247} with dose-response relationships for both smoking frequency and duration.^{Endnote 86, Endnote 248} As previously mentioned, reductions in smoking prevalence occurred 20 years earlier in males than in females in Canada.^{Endnote 42, Endnote 43} The impact of the reduction in tobacco consumption has been presented in the observed incidence data for males, and accordingly contributed to the predicted declining incidence trends, but has largely not yet been seen in the female trends given the lag of 20 to 30 years between the drop in smoking rates and subsequent decrease in cancer incidence rates.^{Endnote 249} Consequently, incidence rates of bladder cancer in females are likely to begin to decrease over the longer term.

Epidemiological studies have linked bladder cancer to occupational exposures for over 100 years.^{Endnote 248} A case-control study in Montreal reported that 6.5% of bladder cancer incidence were attributed to occupational exposures (including motor vehicle drivers, textile dyers, motor transport and aromatic amines).^{Endnote 250} Another Canadian study found statistically significant increased risks of bladder cancer in male primary metal workers and automechanics, and female general office clerks, with a duration-response effect.^{Endnote 251}

Two pooled analyses of epidemiological studies, conducted in Canada, the US, Finland, France and Italy, found a significant association between tap water consumption and risk of bladder cancer, particularly in males.^{Endnote 252, Endnote 253} The summarized dose-response relation suggests that carcinogenic chemicals (such as chloroform and other trihalomethanes) in tap water are responsible for the increased risk.