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

Chapter 4: Projections by Cancer Site

2. Esophagus cancer

Esophageal cancer is infrequent but very malignant. The average annual number of new esophageal cancer cases in 2003–2007 was 1095 in males and 385 in females (Tables 4.2.1 and 4.2.2), constituting 1.4% and 0.5% of all male and female cancer cases, respectively.

From 1983–1987 to 2003–2007, the ASIRs of esophageal cancer in Canada increased by 6.9% in males, from 5.8 to 6.2 per 100 000, and decreased by 10.5% in females, from 1.9 to 1.7 per 100 000 (Figure 4.2.1). In recent years, the ASIRs have remained relatively stable (Figures 3.1 and 3.2). The distribution of morphology in Canada in 2002–2006 for adenocarcinoma, squamous cell carcinoma, and other and unknown types was 56%, 30% and 14% in males and 28%, 53% and 19% in females, respectively.^{Endnote 61} Survival is poor, with a 5-year relative survival rate of 14% in 2006–2008.^{Endnote 1}

From 2003–2007 to 2028–2032, the ASIRs of esophageal cancer for the country are projected to remain stable, at 6.2 per 100 000 in males and at 1.7 per 100 000 in females (Tables 4.2.3 and 4.2.4).

Because of the aging and growth of the Canadian population, the annual number of new male cases is projected to increase by 93%, from 1095 to 2110, and of new female cases by 79%, from 385 to 690 (Tables 4.2.1 and 4.2.2). The overall stable ASIRs are expected to continue in both sexes for all age groups, the only exception being an increase in males younger than 55 (Figure 4.2.2). Random error from the few cases in this age group could potentially influence the accuracy of this finding.

In 2003–2007, incidence rates for esophageal cancer increased steeply with age: most of the cases occurred in people aged 55 or older (85% in males and 92% in females). In the same period, the overall ASIRs for esophageal cancer were 3.6 times greater for males than for females. By age group, the male-to-female rate ratio of esophageal cancer at the national level decreased with age from 5.3:1 in the 45–54 age group to 2.2:1 in those 85 and older. This pattern is projected to continue over the projection period.

Across all regions of Canada and all periods shown in Tables 4.2.3 and 4.2.4, the average ASIRs of esophageal cancer range from 5.0 (Saskatchewan) to 8.4 (Nova Scotia) per 100 000 in males and from 0.8 (Newfoundland and Labrador) to 2.3 (British Columbia) per 100 000 in females. These differences are likely related to the combined effects of variation in risk factor prevalence and cancer registry practices. Figure 4.2.1 shows the differences in ASIRs by broader areas. In males, the Atlantic region is projected to have about 18% higher rates than the Prairies and between 25% and 28% higher rates than other regions, where the rates are trending to the same level after 2023–2027. The predictions indicate that rates will slightly increase in the Atlantic and Prairie regions, and remain stable in other regions.

In females, the rates in British Columbia are predicted to be between 42% and 75% higher than those in the other regions. This is notable given that British Columbia generally has lower than national average rates for most cancers. Quebec is projected to continue to have the lowest rates of esophageal cancer. Incidence rates for females have and will continue to decrease steadily from 1993–1997 rates in the Prairies, in Quebec, and most markedly in Ontario. In contrast, the rates in British Columbia are projected to increase marginally. The increase in rates of esophageal cancer is less evident for females than for males in Atlantic Canada.

Comments

While overall incidence rate has stabilized over the past 2 decades, the 2 main types of esophageal cancer demonstrate opposite trends. Adenocarcinoma incidence rose by 4% per year, whereas squamous cell carcinoma incidence decreased by 3% per year from 1986 to 2006.^{Endnote 61} Similar incidence trends have been observed in Australia, the US, and parts of Europe.^{Endnote 62, Endnote 63} Furthermore, the observation that the increase is also seen in more recent birth cohorts would suggest that adenocarcinoma incidence will continue to increase in the years to come.^{Endnote 64} The observed trends may be linked to changes in risk factors, which include smoking, alcohol use, overweight (body mass index [BMI]: 25–29 kg/m²) and obesity (BMI ≥ 30 kg/m²), and insufficient intake of fruit and vegetables.

Tobacco smoking and alcohol drinking are the main risk factors for this cancer, with a stronger association with squamous cell carcinoma than with adenocarcinoma.^{Endnote 65, Endnote 66} In a US case-control study, ever smoking, alcohol use, and low fruit and vegetable consumption were linked to 56.9% (95% confidence interval [CI]: 36.6%–75.1%), 72.4% (CI: 53.3%–85.8%) and 28.7% (CI: 11.1%–56.5%) of squamous cell carcinoma cases, respectively.^{Endnote 67} Reduced smoking in Canada may contribute to the decreasing incidence of squamous cell carcinoma.^{Endnote 43, Endnote 61} About 55% of male esophageal cancers and 44% of female esophageal cancers could be avoided if smoking were eliminated, as could 40% and 30% of such cancers in males and females, respectively, if drinking were eliminated.^{Endnote 3}

The increasing prevalence of gastroesophageal reflux disease (GERD) and obesity is thought to add to the changes in incidence of esophageal cancer. An important risk factor for adenocarcinoma is GERD and the associated development of Barrett's esophagus. ^{Endnote 68} In Western countries, the prevalence of GERD ranges from 10% to 20% of the population.^{Endnote 69} Obesity causally increases risk of adenocarcinoma,^{Endnote 70, Endnote 71} and the link is greater than that of any other obesity-associated cancer.^{Endnote 68} A proposed mechanism is that obesity increases intra-abdominal pressure and gastroesophageal reflux.^{Endnote 68} In contrast to adenocarcinoma, increased BMI may reduce the risk of squamous cell carcinoma.^{Endnote 70, Endnote 71} 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} The prevalence of GERD has increased significantly in Western populations in recent decades^{Endnote 74} and likely continues to increase because of the aging of the population^{Endnote 69} and the increased prevalence of obesity. The observed slight increase in esophagus cancer incidence in males may reflect these changes in the prevalence of GERD and obesity in Canada, as adenocarcinoma accounts for a majority of all male esophageal cancer cases.^{Endnote 61} The increased prevalence of obesity might play a part in the decrease of squamous cell carcinoma incidence, and therefore the slight decrease of overall esophagus cancer rates in females.

The high incidence rates of esophagus cancer in females in British Columbia could partially be explained by high number of immigrants from South Asia and China where hepatitis B virus (HBV) is endemic (see the detailed explanations in Chapter 5).^{Endnote 75, Endnote 76, Endnote 77, Endnote 78}