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

Chapter 4: Projections by Cancer Site

23. Leukemia

Leukemia is the second most common lymphohematopoietic cancer diagnosed in Canadians, after NHL. During 2003–2007, the average annual number of new leukemia cases was 2570 for males and 1875 for females, making up 3.2% and 2.5% of all new male and female cancer cases, respectively (Tables 4.23.1 and 4.23.2).

TABLE 4.23.1
Observed (2003–2007) and projected average annual new cases by age and province/territories combined (TC), leukemia, males, Canada, 2003–2032
Period Age New cases
CA BC AB SK MB ON QC NB NS PE NL TC

Abbreviations: AB, Alberta; BC, British Columbia; CA, Canada; MB, Manitoba; NB, New Brunswick; NL, Newfoundland and Labrador; NS, Nova Scotia; ON, Ontario; PE, Prince Edward Island; QC, Quebec; SK, Saskatchewan; TC, All Territories (Yukon, Northwest Territories and Nunavut).

Note: Totals may not add up due to rounding.

2003–07 <45 395 45 45 15 10 165 85 10 10 5 5 0
45–54 265 35 30 10 10 105 50 5 10 0 5 0
55–64 460 65 45 15 15 190 95 10 15 5 5 0
65–74 615 80 55 20 25 245 150 15 20 5 5 0
75–84 620 80 55 25 25 250 155 10 15 5 0 0
85+ 215 30 15 10 10 75 60 5 5 0 0 0
Total 2570 330 250 100 95 1030 600 55 75 15 20 5
2008–12 <45 415 50 50 15 10 180 90 5 10 0 5 0
45–54 300 40 35 10 10 135 55 5 10 0 0 0
55–64 570 75 65 20 20 230 115 20 20 5 5 0
65–74 710 90 65 25 25 290 170 15 20 5 5 0
75–84 695 90 65 25 25 275 180 10 15 5 5 0
85+ 285 45 20 10 10 115 75 5 5 0 0 0
Total 2980 390 295 105 100 1220 680 60 80 15 20 5
2013–17 <45 440 55 50 20 15 190 90 10 10 0 5 0
45–54 310 40 35 10 5 145 55 5 10 0 0 0
55–64 660 85 75 20 25 275 125 20 20 5 5 0
65–74 885 120 85 25 35 365 200 20 25 5 5 0
75–84 780 105 70 25 25 315 195 15 20 5 5 0
85+ 365 55 30 10 15 145 100 5 10 0 0 0
Total 3440 450 350 110 115 1430 775 70 90 15 20 5
2018–22 <45 465 60 50 20 15 205 95 10 10 0 5 0
45–54 295 35 35 10 5 140 50 0 5 0 0 0
55–64 725 90 85 20 20 320 135 15 25 5 5 0
65–74 1095 145 115 25 40 450 235 30 30 5 5 0
75–84 940 125 85 25 30 385 235 15 20 5 5 0
85+ 430 65 35 10 15 170 120 5 10 0 0 0
Total 3950 520 410 115 125 1675 870 80 100 15 20 5
2023–27 <45 485 65 55 20 15 215 95 10 10 0 5 0
45–54 295 35 30 10 5 140 55 0 5 0 0 0
55–64 740 95 85 20 20 340 135 10 20 5 5 0
65–74 1270 165 145 25 45 535 265 35 35 5 5 0
75–84 1210 165 120 30 40 495 285 25 30 5 5 0
85+ 515 75 45 15 15 215 135 5 10 0 0 0
Total 4515 595 480 120 145 1940 975 90 115 20 25 10
2028–32 <45 500 65 55 20 15 225 100 10 10 0 5 0
45–54 320 45 35 10 10 150 60 5 5 0 0 0
55–64 705 85 85 20 20 330 125 10 20 5 5 0
65–74 1410 180 160 30 45 625 280 30 35 5 5 0
75–84 1515 205 160 35 50 620 345 35 40 5 5 0
85+ 645 95 55 10 20 265 175 10 15 5 0 0
Total 5095 680 550 125 160 2220 1085 95 125 20 25 10
TABLE 4.23.2
Observed (2003–2007) and projected average annual new cases by age and province/territories combined (TC), leukemia, females, Canada, 2003–2032
Period Age New cases
CA BC AB SK MB ON QC NB NS PE NL TC

Abbreviations: AB, Alberta; BC, British Columbia; CA, Canada; MB, Manitoba; NB, New Brunswick; NL, Newfoundland and Labrador; NS, Nova Scotia; ON, Ontario; PE, Prince Edward Island; QC, Quebec; SK, Saskatchewan; TC, All Territories (Yukon, Northwest Territories and Nunavut).

Note: Totals may not add up due to rounding.

2003–07 <45 300 35 35 10 10 120 65 5 5 0 5 0
45–54 180 20 20 10 5 75 35 5 5 0 0 0
55–64 280 35 30 10 15 110 60 5 10 0 5 0
65–74 390 50 35 15 15 155 95 10 10 0 0 0
75–84 480 55 40 20 20 190 125 10 15 0 0 0
85+ 250 35 15 10 10 95 75 5 10 0 0 0
Total 1875 230 175 70 75 750 455 40 55 10 15 5
2008–12 <45 315 35 35 10 10 135 70 5 5 0 5 0
45–54 200 25 20 10 5 85 40 5 5 0 0 0
55–64 335 40 35 10 15 145 65 5 10 0 5 0
65–74 450 55 45 15 15 185 105 10 10 0 5 0
75–84 520 65 50 20 15 210 135 10 15 0 0 0
85+ 340 45 25 10 15 135 100 5 10 0 0 0
Total 2155 270 205 75 75 895 510 50 55 10 15 5
2013–17 <45 330 40 35 10 10 140 70 5 5 0 5 0
45–54 200 25 20 10 5 95 35 10 5 0 0 0
55–64 380 45 40 15 15 170 75 10 10 0 5 0
65–74 565 75 55 15 25 230 125 15 15 0 5 0
75–84 565 70 55 20 15 235 145 10 15 0 5 0
85+ 400 60 30 10 15 160 110 5 10 0 0 0
Total 2445 310 240 80 80 1035 560 55 60 10 20 5
2018–22 <45 345 45 35 10 10 150 75 5 5 0 5 0
45–54 195 20 20 5 5 100 35 10 5 0 0 0
55–64 425 50 50 20 15 195 75 15 10 0 5 0
65–74 670 90 70 20 25 285 140 15 20 5 5 0
75–84 680 85 65 20 20 280 165 15 20 5 5 0
85+ 455 65 40 10 15 180 125 10 10 0 0 0
Total 2770 355 280 90 90 1190 615 65 70 10 20 5
2023–27 <45 360 45 35 10 10 160 75 5 5 0 5 0
45–54 200 20 20 5 5 95 40 5 5 0 0 0
55–64 430 50 50 20 15 210 70 15 10 0 5 0
65–74 765 100 80 30 25 335 160 20 20 5 5 0
75–84 855 115 85 25 30 355 200 20 25 5 5 0
85+ 520 75 45 10 15 215 140 10 15 5 0 0
Total 3130 405 320 100 100 1365 680 75 75 15 20 5
2028–32 <45 370 50 35 10 10 165 75 5 5 0 5 0
45–54 205 20 20 10 5 95 45 5 5 0 0 0
55–64 415 45 45 15 10 215 70 15 10 0 5 0
65–74 855 105 90 35 30 380 165 25 20 5 5 0
75–84 1025 140 110 30 35 440 225 20 30 5 5 0
85+ 645 100 55 15 20 260 165 15 15 5 0 0
Total 3520 460 360 115 115 1555 745 85 85 15 25 10

The lifetime risk of developing leukemia is 1 in 53 for males and 1 in 72 for females.Endnote 1 The lifetime probability of dying from the disease is 1 in 96 for males and 1 in 125 for females. The 5-year relative survival rate for leukemia is intermediate among cancers, at 59% in males and females for 2006–2008 in Canada.Endnote 1

Leukemia is the most frequently diagnosed childhood malignancy, representing 72% of the lymphohematopoietic cancers in children and youth aged 0 to 14, and 33% of all childhood cancers in Canada during 2003–2007 (data not shown). Figure 4.23.1 shows how age-specific incidence rates varied with age in 2003–2007. The incidence rate had a small peak in children aged 0 to 4, then decreased and remained stable until age 30 when it started to increase slowly to the early 50s. The rate then escalated rapidly and reached its peak in people aged 85 and over. Almost three-quarters (74%) of leukemia cases occurred in those aged 55 or older. Males and females had similar rates up to age 50, after which the rates were higher in males and the divergence between sexes increased consistently with advancing age (Figure 4.23.1). The male-to- female ratio of ASIRs increased steadily from 1.3:1 in the under 45 age group to 1.9:1 in those aged 85 or older.

FIGURE 4.23.1
Age-specific incidence rates of leukemia, Canada, 2003–2007 (from average annual counts)

Age-specific incidence rates of leukemia, Canada, 2003–2007 (from average annual counts)

[Click to enlarge]

[FIGURE 4.23.1, Text Equivalent]

Health Promotion and Chronic Disease Prevention in Canada - Volume 35 · Supplement 1 · Spring 2015

FIGURE 4.23.1
Age-specific incidence rates of leukemia, Canada, 2003-2007 (from average annual counts)

Figure 4.23.1 shows how age-specific incidence rates of leukemia varied with age in 2003-2007. The incidence rate had a small peak in children aged 0 to 4, then decreased and remained stable until age 30 when it started to increase slowly to the early 50s. The rate then escalated rapidly and reached its peak in people aged 85 and over. Males and females had similar rates up to age 50, after which the rates were higher in males and the divergence between sexes increased consistently with advancing age.

The overall ASIRs for leukemia decreased slightly from 1983–1987 until 1993–1997 (Figure 4.23.2). Thereafter, the incidence rates increased slightly to the same level in 2003–2007 as in the earliest observation period 20 years before. During 1998–2007, leukemia ASIRs increased non-significantly in males by 0.6% per year and increased significantly in females by 1.2% per year (Figures 3.1 and 3.2). Most of the increases occurred in men aged 65 or older and in women aged 65 to 74. The regional trends in ASIRs of leukemia were very similar for males and females (Figure 4.23.2). In the last observation period (2003–2007), the internal ranking of the regional ASIRs was similar for males and females, with significantly low rates in Atlantic Canada and elevated rates in the Prairies.

FIGURE 4.23.2
Age-standardized incidence rates (ASIRs) by region, leukemia, 1983–2032

Age-standardized incidence rates (ASIRs) by region, leukemia, 1983–2032

[Click to enlarge]

[FIGURE 4.23.2, Text Equivalent]

Health Promotion and Chronic Disease Prevention in Canada - Volume 35 · Supplement 1 · Spring 2015

FIGURE 4.23.2
Age-standardized incidence rates (ASIRs) by region, leukemia, 1983-2032

From 2003-2007 to 2028-2032, the leukemia ASIRs for Canada are projected to increase marginally in both sexes. The predicted regional trends of leukemia ASIRs are similar in males and females. The ASIRs are expected to increase slightly in British Columbia, in the Atlantic region, and most evidently in Ontario. The rates will decrease marginally or stabilize in the Prairies and Quebec. The ranking of the regions in ASIRs will be the same for males and females. The rates for Ontario are projected to surpass those for the Prairies within the next 5 years. The Atlantic region will continue to experience the lowest rates.

The predicted regional trends of leukemia ASIRs are similar in males and females (Figure 4.23.2). The ASIRs are expected to increase slightly in British Columbia, in the Atlantic region, and most evidently in Ontario. The rates will decrease marginally or stabilize in the Prairies and Quebec. The ranking of the regions in ASIRs will be the same for males and females. The rates for Ontario are projected to surpass those for the Prairies within the next 5 years. The Atlantic region will continue to experience the lowest rates. Figure 4.23.3 shows that the ASIRs of leukemia are predicted to increase or level off across the age groups but the difference between males and females persists over time.

FIGURE 4.23.3
Age-standardized incidence rates (ASIRs) for leukemia by age group, Canada, 1983–2032 (red lines denote males, blue lines denote females)

Age-standardized incidence rates (ASIRs) for leukemia by age group (males, females), Canada, 1983–2032

[Click to enlarge]

[FIGURE 4.23.3, Text Equivalent]

Health Promotion and Chronic Disease Prevention in Canada - Volume 35 · Supplement 1 · Spring 2015

FIGURE 4.23.3
Age-standardized incidence rates (ASIRs) for leukemia by age group, Canada, 1983-2032

Figure 4.23.3 shows that the ASIRs of leukemia are predicted to increase or level off across the age groups but the difference between males and females persists over time.

From 2003–2007 to 2028–2032, leukemia ASIRs for Canada are projected to increase by 5% in males, from 15.1 to 15.8 per 100 000, and by 7% in females, from 9.2 to 9.8 per 100 000 (Tables 4.23.3 and 4.23.4).

TABLE 4.23.3
Observed (2003–2007) and projected age-standardized incidence rates (ASIRs) by age and province/territories combined (TC), leukemia, males, Canada, 2003–2032
Period Age ASIRs
CA BC AB SK MB ON QC NB NS PE NL TC

Abbreviations: AB, Alberta; BC, British Columbia; CA, Canada; MB, Manitoba; NB, New Brunswick; NL, Newfoundland and Labrador; NS, Nova Scotia; ON, Ontario; PE, Prince Edward Island; QC, Quebec; SK, Saskatchewan; TC, All Territories (Yukon, Northwest Territories and Nunavut).

2003–07 <45 4.0 3.8 4.2 5.5 3.0 4.2 3.8 4.0 3.7 6.3 3.5 3.1
45–54 10.6 10.2 12.3 12.1 13.5 11.5 8.3 9.9 11.8 19.4 6.2 17.8
55–64 26.9 27.0 30.3 33.1 25.2 29.5 21.9 27.0 29.2 36.0 15.5 14.5
65–74 57.0 51.5 62.2 63.8 62.5 59.8 56.4 49.0 52.6 77.5 17.0 32.8
75–84 100.1 86.6 104.6 107.7 104.0 104.1 108.7 66.7 83.3 132.0 20.8 61.3
85+ 139.3 116.6 115.9 141.1 153.0 133.1 194.9 82.6 108.1 132.8 17.9 145.1
Total 15.1 13.9 16.0 17.6 15.3 15.8 15.1 12.7 14.0 20.9 6.5 11.2
2008–12 <45 4.2 4.0 3.9 5.6 3.2 4.6 4.0 3.7 3.8 4.2 3.6 3.1
45–54 11.0 10.3 11.5 12.5 9.4 12.8 8.4 6.9 12.4 11.2 5.3 8.1
55–64 27.7 26.4 31.6 30.9 28.2 30.3 22.4 33.9 29.8 28.2 12.7 20.4
65–74 57.2 51.8 62.5 63.1 65.8 62.4 53.7 44.7 45.9 55.0 19.8 42.1
75–84 99.2 89.2 109.0 110.8 91.2 101.0 107.7 71.6 81.8 97.6 24.4 72.9
85+ 135.9 131.5 113.9 132.4 128.2 140.1 165.5 68.5 115.8 131.0 27.3 99.9
Total 15.3 14.2 16.0 17.5 14.7 16.4 14.8 12.5 13.8 15.1 6.6 11.3
2013–17 <45 4.2 4.0 3.8 5.9 3.2 4.7 4.0 3.9 3.9 4.2 3.6 3.1
45–54 11.4 10.5 11.6 14.7 7.7 13.3 8.9 4.9 11.7 11.2 5.2 8.4
55–64 28.1 26.5 31.7 26.4 27.7 31.2 22.5 35.7 31.2 28.4 12.5 20.6
65–74 56.8 52.7 62.6 54.2 63.9 62.4 51.9 52.5 45.7 55.3 19.6 41.8
75–84 101.0 90.1 108.1 111.0 99.7 106.7 104.2 67.3 80.4 98.2 24.0 74.3
85+ 136.8 130.3 139.5 117.8 126.5 135.4 170.4 71.5 122.0 131.4 27.0 100.6
Total 15.5 14.3 16.2 16.8 14.6 16.8 14.7 13.0 13.9 15.2 6.6 11.4
2018–22 <45 4.3 4.1 3.8 6.0 3.2 4.8 4.1 4.0 4.0 4.3 3.6 3.2
45–54 11.5 9.9 11.7 16.2 8.1 13.8 9.1 4.7 10.8 11.4 5.2 8.5
55–64 28.0 25.7 30.9 26.3 25.0 31.9 21.9 26.8 31.0 28.7 12.4 20.5
65–74 57.7 53.2 64.4 48.6 61.4 63.5 51.5 64.3 49.2 56.1 19.4 42.4
75–84 101.1 91.8 107.8 98.6 106.7 109.1 101.8 69.1 77.7 99.2 23.8 74.3
85+ 136.0 130.7 131.0 120.7 119.4 136.9 166.2 77.0 114.2 133.2 26.8 100.0
Total 15.6 14.4 16.2 16.2 14.5 17.2 14.5 13.2 13.9 15.4 6.5 11.5
2023–27 <45 4.3 4.2 3.9 5.8 3.3 4.9 4.1 4.2 4.0 4.3 3.6 3.2
45–54 11.6 9.9 10.7 17.7 7.8 14.2 9.6 4.9 11.1 11.4 5.2 8.6
55–64 28.6 25.8 31.4 30.3 21.2 32.7 22.7 20.5 29.4 28.9 12.4 21.0
65–74 58.1 53.1 64.9 41.8 61.3 64.6 51.3 65.2 51.0 56.2 19.3 42.7
75–84 100.4 92.9 109.2 86.0 104.4 108.5 98.5 81.2 78.4 99.6 23.7 73.8
85+ 140.4 132.1 136.3 118.1 143.4 147.0 160.5 67.3 116.6 133.9 26.7 103.2
Total 15.7 14.5 16.2 15.7 14.4 17.5 14.5 13.2 14.0 15.4 6.5 11.5
2028–32 <45 4.4 4.1 3.9 6.2 3.3 4.9 4.1 4.5 4.0 4.3 3.6 3.2
45–54 11.9 11.5 10.5 15.6 8.5 14.4 9.7 4.9 11.7 11.4 5.1 8.8
55–64 29.0 24.7 31.8 32.6 22.1 33.6 23.4 20.1 27.6 29.0 12.3 21.3
65–74 57.8 51.5 63.6 43.4 55.6 65.6 50.3 49.5 50.8 56.6 19.2 42.5
75–84 101.9 93.5 112.2 77.4 101.5 110.1 98.5 98.7 83.8 100.1 23.6 74.9
85+ 137.1 134.8 132.5 96.6 143.4 144.1 158.6 77.2 109.0 134.3 26.5 100.7
Total 15.8 14.5 16.3 15.5 14.0 17.7 14.5 13.1 14.0 15.5 6.5 11.6
TABLE 4.23.4
Observed (2003–2007) and projected age-standardized incidence rates (ASIRs) by age and province/territories combined (TC), leukemia, females, Canada, 2003–2032
Period Age ASIRs
CA BC AB SK MB ON QC NB NS PE NL TC

Abbreviations: AB, Alberta; BC, British Columbia; CA, Canada; MB, Manitoba; NB, New Brunswick; NL, Newfoundland and Labrador; NS, Nova Scotia; ON, Ontario; PE, Prince Edward Island; QC, Quebec; SK, Saskatchewan; TC, All Territories (Yukon, Northwest Territories and Nunavut).

2003–07 <45 3.1 2.9 3.3 3.2 3.0 3.2 3.1 3.4 2.5 3.6 3.2 3.7
45–54 7.1 6.1 7.3 10.8 7.6 8.1 6.0 8.2 5.5 5.5 4.1 0.0
55–64 15.9 14.7 20.4 20.4 22.6 16.8 13.1 12.5 15.7 14.5 10.3 20.4
65–74 32.4 30.7 37.2 38.8 31.0 33.8 31.1 31.6 29.3 32.8 9.0 39.5
75–84 54.3 48.7 57.8 55.6 57.3 56.0 56.6 43.3 53.7 55.4 16.6 61.8
85+ 73.6 69.5 54.0 61.2 58.6 75.7 91.0 48.2 78.2 75.1 11.8 0.0
Total 9.2 8.5 10.0 10.4 9.6 9.6 9.0 8.5 8.4 9.3 4.9 9.2
2008–12 <45 3.3 3.1 2.9 3.4 2.5 3.5 3.2 3.6 2.6 3.4 2.9 3.1
45–54 7.3 6.2 7.5 10.9 7.3 8.1 6.0 11.7 5.7 7.1 5.3 6.8
55–64 15.7 14.2 18.9 19.1 18.9 18.0 12.4 13.0 14.8 14.6 9.6 15.0
65–74 33.3 30.8 39.4 38.3 37.1 35.6 30.6 30.8 26.4 26.7 14.5 30.8
75–84 56.4 51.3 64.7 64.0 50.1 58.8 57.0 52.3 54.3 45.9 17.4 55.4
85+ 78.3 76.9 64.8 65.2 67.1 81.0 94.3 46.4 67.1 72.1 13.6 71.5
Total 9.5 8.7 10.1 10.7 9.2 10.2 9.0 9.3 8.1 8.6 5.1 9.0
2013–17 <45 3.3 3.0 2.9 3.4 2.5 3.6 3.3 3.4 2.5 3.7 3.0 3.1
45–54 7.5 6.3 7.4 10.9 7.7 9.0 5.8 13.5 5.7 7.3 5.5 6.9
55–64 15.7 13.5 17.4 22.6 15.5 18.6 12.4 15.6 14.3 14.6 9.8 15.1
65–74 33.5 31.8 38.7 37.6 40.8 36.1 29.8 33.2 26.6 26.6 14.9 31.1
75–84 58.3 53.0 69.0 62.0 50.9 62.0 58.1 47.7 53.3 46.8 17.8 56.0
85+ 78.5 82.6 74.3 67.1 63.5 82.5 86.6 55.8 69.1 74.4 14.0 72.3
Total 9.6 8.8 10.2 11.0 9.1 10.6 9.0 9.7 8.0 8.9 5.3 9.1
2018–22 <45 3.3 3.1 2.8 3.5 2.5 3.6 3.2 3.4 2.3 4.1 3.0 3.2
45–54 7.8 5.7 7.4 10.0 6.0 9.5 6.8 14.6 5.3 7.7 5.6 7.1
55–64 16.1 13.0 18.0 27.5 16.9 18.9 12.5 20.5 13.6 14.7 10.0 15.4
65–74 32.7 30.9 36.9 35.5 36.3 36.8 28.3 30.1 27.0 26.4 15.1 31.7
75–84 60.1 55.9 69.1 64.9 58.7 64.9 57.7 49.0 52.0 47.0 18.1 57.0
85+ 80.9 86.3 81.5 64.7 65.1 83.1 88.3 75.3 76.3 76.3 14.2 73.6
Total 9.7 8.9 10.1 11.3 9.1 10.8 8.9 10.3 7.9 9.2 5.4 9.3
2023–27 <45 3.3 3.2 2.7 3.6 2.3 3.6 3.2 3.6 2.3 4.6 3.1 3.2
45–54 7.9 5.2 7.9 10.0 6.4 9.1 7.6 12.6 5.5 8.2 5.6 7.0
55–64 16.5 13.2 18.0 27.5 18.3 20.1 11.9 23.3 13.9 15.1 10.1 15.5
65–74 32.7 29.4 34.7 41.9 32.0 37.4 28.5 35.7 26.5 26.2 15.2 31.8
75–84 59.8 57.1 68.5 62.0 64.2 64.7 56.2 50.8 52.8 46.7 18.2 57.3
85+ 83.0 87.8 85.4 62.8 67.0 88.9 89.5 50.9 69.7 77.1 14.3 73.4
Total 9.8 8.8 10.0 11.7 9.0 11.0 8.9 10.6 7.8 9.6 5.4 9.3
2028–32 <45 3.3 3.2 2.8 3.7 2.2 3.7 3.2 3.6 2.3 5.1 3.1 3.3
45–54 7.7 5.6 7.0 10.3 8.1 8.5 7.5 11.3 4.6 9.0 5.7 7.2
55–64 17.0 12.2 17.8 25.6 15.0 21.1 13.5 24.8 13.2 15.9 10.2 15.7
65–74 33.3 28.8 36.1 49.2 36.0 37.7 28.2 44.5 25.5 26.5 15.4 32.3
75–84 58.6 55.6 65.3 60.1 57.4 65.9 53.4 46.7 53.9 46.2 18.4 58.2
85+ 85.2 94.3 83.0 68.8 83.0 90.4 87.5 70.8 72.3 77.1 14.5 75.2
Total 9.8 8.8 9.8 12.1 9.0 11.1 8.9 11.3 7.7 10.1 5.5 9.5

The annual number of newly diagnosed male cases is projected to increase by 98%, from 2570 to 5095, and the number of new female cases, by 88%, from 1875 to 3520 (Tables 4.23.1 and 4.23.2).

Comments

Leukemia is a cancer of the white blood cells. It has 4 main subtypes: acute lymphocytic leukemia (ALL), chronic lymphocytic leukemia (CLL), acute myeloid leukemia (AML) and chronic myeloid leukemia (CML).

The overall observed incidence rates for leukemia were generally modest, decreasing slightly during 1983–1997 and then increasing slightly, a pattern consistent with that observed in the US.Endnote 293 The etiology of leukemia remains largely unknown. The established and suspected risk factors include environmental exposures, genetic (inherited) susceptibility and lifestyle category.

In 2008, IARC documented that exposure to ionizing radiation, alkylating agents (used in chemotherapy) and benzene had been consistently associated with leukemia risk.Endnote 86 Ionizing radiation is linked to increased incidence of AML, ALL and CML, but not CLL. Exposures include atomic bomb exposure (Hiroshima and Nagasaki), nuclear power plant accidents and therapeutic radiation exposure. Endnote 52, Endnote 53, Endnote 86, Endnote 294, Endnote 295 Findings from exposure to electromagnetic fields are inconsistent. IARC has concluded that occupational benzene exposure causes leukemia, particularly AML.Endnote 47, Endnote 86 Benzene is also present in tobacco smoke and gasoline. Smoking, accounting for 20% of AML cases, is associated with a 2-fold increase in AML risk including in a Canadian cohort.Endnote 52, Endnote 111, Endnote 295, Endnote 296 The prevalence of these exposures has been stable or decreasing during the study period and can explain the relative stable and the decreased component of the incidence trend of leukemia.

Viruses, particularly retroviruses, have been linked to the development of leukemia. IARC considers HTLV-1 infection to be causally associated with leukemia.Endnote 47 HTLV-1 infects 5 to 10 million people in the world, Endnote 297 with clusters in certain ethnic/ geographical concentrations in Japan, Africa, South America, the Caribbean and Melanesia.Endnote 297, Endnote 298 EBV is the etiological agent of acute infectious mononucleosis and is associated with adult ALL and aggressive NK-cell leukemia.Endnote 53, Endnote 298, Endnote 299

Some identified chromosomal anomalies are related to leukemia. CLL, the most common adult leukemia in the West, is estimated to have one of the highest familial risks for a hematological malignancy. Endnote 300 A 7.5-fold increased risk of CLL has been observed in people with a first degree relative with CLL.Endnote 301 Cytogenetic abnormalities occur in around 50% of CLL cases.Endnote 302 A reciprocal chromosomal translocation known as the Philadelphia chromosome is present in 95% of CML cases.Endnote 303 Philadelphia chromosome is also seen in about 20% to 30% of adult ALL cases.Endnote 304 Children with Down syndrome have a 10- to 30-fold increased risk of ALL and AML.Endnote 52, Endnote 53, Endnote 111, Endnote 294, Endnote 305 Inherited genetic syndromes have been linked to 5% of ALL and AML cases.Endnote 306

Lifestyle factors have been implicated in the development of leukemia.Endnote 307 A meta-analysis showed an increased risk for each of the 4 major subtypes of leukemia in obese people.Endnote 308 A Canadian case-control study estimated that, compared with normal weight, the odds ratios of leukemia were 1.3 (95% CI: 1.1–1.5) for overweight and 1.6 (CI: 1.3–2.0) for obesity.Endnote 309 Overweight and obesity together accounted for 18% of all leukemias in Canada—9% from overweight and 8% from obesity.Endnote 309 The prevalence of obesity has increased in Canada.Endnote 51, Endnote 72, Endnote 73, Endnote 110 However, current data are not sufficient to conclude whether the increased prevalence of obesity explains some of the recent increase in leukemia incidence. Based on the same populationbased Canadian data, the researchers observed a 25% risk reduction for adult leukemia associated with the highest category of vigorous physical activity (OR = 0.75; CI: 0.57–0.99). Risk reductions associated with high levels of vigorous activity were greater with higher BMI.Endnote 310

Changes in coding practice and the clinical ability to identify leukemia may contribute to some of the increase. In addition, changes in classification could also influence the trends.Endnote 295

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