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  • A previous analysis of future cancer incidence trends in Can

    2019-08-20

    A previous analysis of future cancer incidence trends in Canada estimated that the ASIR for colorectal cancer in men would decrease slightly to 57.0/100,000 in men and 38.6/100,000 in women by 2028–2032 [3]. Our estimates suggest that although the ASIRs for colorectal cancer in men and women have been decreasing, the rates will increase after 2013 and continue to rise. This increase in colorectal cancer in Canada is likely attributable to various factors, which may include the projected increasing prevalence of obesity and reduced levels of physical activity [22], as obesity is known to be associated with colorectal cancer [23]. Sub-optimal colorectal cancer screening uptake (˜55%] in Canada [24] could likely also contributes to the projected increase in colorectal cancer. For lung cancer, previous estimates suggest that the ASIR will decrease to 46.4/100,000 in men and marginally decrease to 39.6/100,000 in women by 2028–2032 [3]. Our estimates are similar, with slightly lower ASIRs for men and a slower decrease for women by 2042. Lung cancer incidence in Canada is largely driven by the prevalence of tobacco smoking, as up to 85% of lung cancer has been shown to be attributable to smoking [[25], [26], [27], [28]]. The delayed decrease in lung cancer incidence rates for women is because the prevalence of smoking in women did not begin to decrease until the mid-1980s, whereas the prevalence of smoking in men began to decrease in the mid-1960s [29]. Consistent with our estimates, the incidence rates of Methoxy-X04 cancer in men and women were previously estimated to decrease slightly and then remain generally stable by 2028-2032 with ASIRs of 24.0/100,000 and 7.3/100,000, respectively [3]. From our analysis, bladder cancer incidence rates are estimated to slightly decrease until 2023 and then remain generally stable to 2042. As with lung cancer, the greatest preventable cause of bladder cancer is smoking, with previous Canadian studies estimating that up to 40% of bladder cancer is attributable to smoking [26,28]. Therefore, as with lung cancer, it is likely that the rate of bladder cancer in women will continue to decrease in the future. Compared to colorectal, lung and breast cancer, the variability in the incidence of bladder cancer, as shown in Fig. 4, seems to be greater between 1983 and 2012. This perceived variability could be due to the lower incidence of bladder cancer cases compared to colorectal, lung and breast cancer, which causes the variability to seem greater, even if the variability across cancer sites is similar. In addition, the variability observed for bladder cancer could stem from differences in registration between 1983 and 2012 and by province. As previously reported [30], there has been a lack of consistency in the reporting on noninvasive (in-situ) bladder tumours over time and although the provincial registries are held to a high standard by the Canadian Cancer Registry, there may have been inconsistencies between 1983 and 2012. Our ASIR projection estimate for female breast cancer of 116.3/100,000 is higher than the previously estimated 98.7/100,000 for 2028–2032 [3]. Although estimates show some plateauing of incidence between 1993 and 2013, the rate of female breast cancer is projected to increase again from 2023 to 2042. The increase in incidence could be explained by various factors. New practice guidelines released in 2013 by the Canadian Association of Radiologists recommend women aged 40 to 49 be screened annually and biennial screening for women between the ages of 50 and 74 [31]. In addition, breast-feeding and parity have been shown to be associated with a reduced risk of breast cancer [32]. Therefore, decreasing fertility rates in Canada [33] could also contribute to the increasing incidence of breast cancer. Finally, we previously estimated that up to 50% of breast cancer is attributable to modifiable factors such as physical inactivity, excess body fat, alcohol consumption and hormone use [34]. Changes in these behaviours on a population level could help explain the increase in incidence of breast cancer in addition to the aging population and longer life spans in Canada [35].