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

Chapter 4: Projections by Cancer Site

5. Liver cancer

In 2003–2007, liver cancer was responsible for 1.3% and 0.5% of all new cancer cases in Canadian males and females, respectively. During this period, the average annual number of new cases of liver cancer was 1025 in males and 350 in females (Tables 4.5.1 and 4.5.2).

While incidence rates for all cancers combined and for most types of cancer are stable or decreasing, liver cancer incidence rates are rising significantly in both sexes. Though rare in Canada, liver cancer is the second fastest increasing cancer in both males and females (after thyroid cancer). Between 1998 and 2007, liver cancer rates rose an average of 3.6% per year in males and 2.4% per year in females (Figures 3.1 and 3.2). Approximately 95% of all liver cancer cases in the last observed period occurred in people aged 45 or older (Tables 4.5.1 and 4.5.2). The overall incidence rate of liver cancer in males was 3.5 times higher than in females (Tables 4.5.3 and 4.5.4).

The male-to-female ratio of the rates ranged between 2.5:1 and 5.1:1 for all age groups. Survival is poor, with a 5-year relative survival rate of 20% in 2006–2008.^{Endnote 1}

Figure 4.5.1 shows that the ASIRs of liver cancer are predicted to increase and eventually plateau in both sexes in all regions except in the Atlantic region for females, where it will stay unchanged. Male incidence rates in Ontario and Quebec are expected to reach a peak after 20 years and then decrease marginally. Female rates are projected to peak in Quebec after 10 years and in the Prairies and for Canada as a whole 5 years later. The rates in Atlantic Canada are predicted to be between 1.5 and 2.3 times lower than in the other regions for both males and females from 2008–2012 to 2028–2032, a result of the increased divergence in the rates over the observed periods. British Columbia is projected to experience the highest incidence rates across the country.

Rates for Canadian men in the 45–54 age group are predicted to have reached a peak already and to decrease until 2028–2032 (Figure 4.5.2). The gap in rates between the sexes will widen over time for those aged 55 or older, peaking in 2013–2017 and 2023–2027 for the 55–64 and 65–74 age groups, respectively.

From 2003–2007 to 2028–2032, the Canadian ASIRs for liver cancer are projected to increase by 43%in males, from 5.7 to 8.2 per 100 000, and by 15% in females, from 1.6 to 1.9 per 100 000 (Tables 4.5.3 and 4.5.4). The annual number of new cases in males is projected to increase by 178%, from 1025 to 2845, and the number of new cases in females is projected to increase by 117%, from 350 to 760 (Tables 4.5.1 and 4.5.2).

Comments

Chronic infection with HBV or hepatitis C virus (HCV) is the primary risk factor for the development of most liver cancers worldwide.^{Endnote 47, Endnote 86, Endnote 96, Endnote 97} A recent report from the Mayo Clinic based on a US cohort suggests the main cause of the increase in liver cancer has been the rise in chronic HCV infection.^{Endnote 97} HCV is much more common than HBV in Canada, with incidence rates in 2000 of 61.0 and 3.2 per 100 000 people, respectively.^{Endnote 98} The incidence rates of HCV for both Canadian males and females increased sharply beginning in 1992, the start of widespread testing for HCV, reached their peaks in 1995, and have since decreased but remained high.^{Endnote 98, Endnote 99} Given a latency period of approximately 20 years between the time of infection with HCV and the onset of liver cancer,^{Endnote 100, Endnote 101} HCV is likely responsible for a substantial proportion of the observed and projected increases in liver cancer incidence. The higher rates of liver cancer in British Columbia may be in part explained by the higher HCV rates in this province.^{Endnote 99}

Although HCV is the leading risk factor for liver cancer in Western countries—especially in Canada—HBV is implicated in over two-thirds of liver cancers in the developing countries.^{Endnote 86} HBV infection accounts for 23% of all hepatocellular carcinoma in developed countries.^{Endnote 1} HBV vaccination in early childhood greatly reduces the likelihood of hepatitis B.^{Endnote 76} Currently, all provinces and territories have a childhood hepatitis B immunization program.^{Endnote 102, Endnote 103} The ongoing increasing trends of liver cancer incidence in Canada, especially in British Columbia, are possibly linked to the increasing immigration from endemic areas of HBV.^{Endnote 75, Endnote 76, Endnote 77, Endnote 78, Endnote 104} The number of immigrants in Canada reached 6.2 million, or 20% of the total population, in 2006, with Asia and the Middle East accounting for 41% of the immigrant population. ^{Endnote 105, Endnote 106} In British Columbia, the proportion of immigrants was 27% of the total provincial population in 2006, with 54% of the immigrant population coming from Asia and the Middle East, and 28% from Eastern Asia, mainly China. East Asia is one of the areas with high HBV prevalence.^{Endnote 76, Endnote 77, Endnote 78} Significantly higher incidence rates of liver cancer have been found in immigrants from South-East Asia and North-East Asia.^{Endnote 104}

Other risk factors include increased rates of alcohol abuse, which increases the risk of liver cirrhosis and therefore the risk of liver cancer, tobacco smoking, diabetes, obesity and non-alcoholic fatty liver disease. ^{Endnote 86, Endnote 107, Endnote 108, Endnote 109} Recent Canadian data suggest that the prevalence rates of obesity have nearly doubled in adults from 1978/79 to 2012.^{Endnote 51, Endnote 72, Endnote 73} This increase may have contributed to the increased incidence trends of liver cancer.^{Endnote 51, Endnote 72, Endnote 73, Endnote 110}