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

Chapter 4: Projections by Cancer Site

16. Kidney cancer

Kidney cancer was the sixth most common type of new cancer diagnosed in Canadian males and the twelfth most common type in females in 2003–2007. The average annual number of kidney cancer cases in this period was 2580 for males and 1665 for females, accounting for 3.2% and 2.2% of all male and female cases, respectively (Tables 4.16.1 and 4.16.2).

One in 56 males and 1 in 82 females can expect to be diagnosed with kidney cancer in their lifetime, and 1 in 149 males and 1 in 252 females can expect to die from it.^{Endnote 1} The 5-year relative survival rate for kidney cancer was 68% for both sexes combined in Canada between 2006 and 2008.^{Endnote 1}

During 2003–2007, the ASIRs of kidney cancer increased with age to 83.1 per 100 000 in men and 43.4 per 100 000 in women for those aged 85 or older, but for those aged 55 or older the increase was less pronounced in women than in men (Tables 4.16.3 and 4.16.4).

Overall, kidney cancer incidence occurred nearly twice as often in males as in females. The male-to-female ratio increased with age in each observation period up to the 65–74 age group and stabilized at almost 2:1 in older age groups (Figure 4.16.2). Tables 4.16.1 and 4.16.2 show that about 90% of cases were diagnosed in people aged 45 or older in 2003–2007.

Figure 4.16.1 shows that incidence rates generally increased in both sexes during the 1980s, stabilized between 1988–1992 and 1993–1997, and rose again after that. In 2003–2007, kidney cancer ASIRs in males increased significantly by 2.6% per year (a change point in trend was detected from 2003, Figure 3.1). During 1998–2007, ASIRs rose significantly in females by 1.9% per year (Figure 3.2). Figure 4.16.2 reveals that incidence of kidney cancer increased over the observation periods across age groups in both sexes, with stronger increases in males in the 1980s and in those (except in the 75–84 age group) during the last 2 observation periods.

The current rising trends in the rates in Canada are projected to continue in each age group (Figure 4.16.2). Figure 4.16.1 shows that the rates of kidney cancer will increase in both sexes in all regions except in British Columbia, where a gradual decrease is predicted, and in the Prairies in females, for whom the rates are forecast to stabilize.

The most elevated rates are predicted for the Atlantic region, while significantly low rates are predicted in British Columbia.

From 2003–2007 to 2028–2032, the ASIRs of kidney cancer for Canada are projected to increase by roughly 7% in both sexes, from 14.4 to 15.5 per 100 000 in males and from 8.0 to 8.6 per 100 000 in females (Tables 4.16.3 and 4.16.4). The annual number of new cases is estimated to increase by 95% in males, from 2580 to 5020, and by 84% in females, from 1665 to 3070 (Tables 4.16.1 and 4.16.2).

Comments

Increases in kidney cancer incidence have been observed in the US, some European countries, Australia, New Zealand and some Asian countries.^{Endnote 224, Endnote 225, Endnote 226, Endnote 227, Endnote 228, Endnote 229, Endnote 230} Although the increasing use of advanced diagnostic imaging systems has probably led to the incidental detection of asymptomatic kidney cancer,^{Endnote 231} the incidence of cancer presenting at a later stage has not decreased.^{Endnote 232} This finding suggests that a true increase in kidney cancer has occurred that cannot be solely attributed to changes in diagnostic practices.^{Endnote 225}

The upward trend in kidney cancer in Canada may be partly explained by changes in risk factors. The major risk factors for kidney cancer include smoking, obesity and some genetic and medical conditions. Smokers have a 50% increase in risk.86 Cigarette smoking is responsible for about 20% to 30% of kidney cancer cases inmales and 10% to 24% of cases in females.^{Endnote 111, Endnote 233, Endnote 234, Endnote 235} Smoking prevalence began to decrease in the mid-1960s in males and in the mid-1980s in females.^{Endnote 42, Endnote 43} Smoking prior to these periods may have contributed to the earlier increases in kidney cancer rates around and immediately following these periods. The reductions in smoking are expected to curb the increase in kidney cancer incidence in the future.

Obesity is a significant risk factor for both sexes, and is responsible for about 20% of renal cell carcinoma cases, the predominant form of kidney cancer.^{Endnote 233, Endnote 235} The prevalence rates of obesity have nearly doubled in adults from 1978/79 to 2012.^{Endnote 51, Endnote 72, Endnote 73} The rates of obesity and kidney cancer have been increasing comparably in Canada in recent decades.

Age-standardized smoking rates and overweight or obese rates have been lower in British Columbia than in other provinces. ^{Endnote 51, Endnote 73} This may partly explain the low incidence rates of kidney cancer in British Columbia.

Hypertension has been linked to an excess risk of 20% to 300%,^{Endnote 233, Endnote 234} with a potential dose-response relationship.^{Endnote 86} Preventing and controlling hypertension may reduce kidney cancer incidence.^{Endnote 236} A meta-analysis of 24 studies suggests that diabetes is associated with an increased risk of kidney cancer, and is independent of alcohol use, obesity and smoking.^{Endnote 237} An increased risk of kidney cancer also has been suggested in patients with acquired renal cystic disease.^{Endnote 238} Hereditary predispositions, characterized as occurring at birth, are responsible for less than 5% of kidney cancer cases.^{Endnote 224, Endnote 239} There is sufficient evidence that trichloroethylene (used primarily for metal degreasing, especially in the aerospace/aircraft industry) causes kidney cancer, according to IARC.^{Endnote 47} The US National Cancer Institute's recent meta-analysis of studies published from 1950 to 2011 indicates a 32% risk increase for occupational trichloroethylene exposure.^{Endnote 240}