Cancer incidence in Canada: trends and projections (1983-2032).

PURPOSE AND INTENDED AUDIENCE: Each year, the Canadian Cancer Statistics publication provides an estimate of expected case counts and rates for common cancer sites for the current year in Canada as a whole and in the provinces and territories. This monograph expands on the Canadian Cancer Statistics publication by providing historical and projected cancer incidence frequencies and rates at national and regional levels from 1983 to 2032. The aim is that this monograph will be an important resource for health researchers and planners. Most importantly, it is hoped the monograph will: - provide evidence-based input for the development of public health policy priorities at the regional and national levels; and - guide public health officials in planning strategy including designing and evaluating preventive interventions and planning resources (treatment requirements) and infrastructure for future cancer control and care intended to reduce the burden of cancer in Canada.

TITRE: Incidence du cancer au Canada : tendances et projections (1983-2032). OBJET ET PUBLICS CIBLES: Chaque année, la publication Statistiques canadiennes sur le cancer donne une estimation du nombre de cas et des taux projetés pour les sièges de cancer courants pour l'année en cours au Canada, dans les provinces et les territoires. La présente monographie vient compléter la publication Statistiques canadiennes sur le cancer en fournissant des projections sur le nombre de nouveaux cas et les taux d'incidence de cancer à l'échelle régionale et nationale de 1983 à 2032. Elle se veut une ressource importante pour les chercheurs et les planificateurs du domaine de la santé. Plus important encore, nous espérons que cette monographie permettra : - de fournir des commentaires fondés sur des données probantes permettant l'élaboration de priorités stratégiques en matière de santé publique à l'échelle régionale et nationale; - de guider les responsables de la santé publique dans la planification d'une stratégie, notamment la conception et l'évaluation d'interventions préventives, ainsi que la planification des ressources (exigences relatives au traitement) et des infrastructures pour assurer la prestation future de soins de santé et de mesures de lutte contre le cancer en vue de réduire le fardeau de la maladie au Canada.

Authors' response.

TITRE: Réponse des auteurs.

Cancer in Canada fact sheet series #1 - thyroid cancer in Canada.

The incidence of thyroid cancer is increasing more rapidly than that of any other cancer in Canada, while mortality has remained low and stable. In the last 10 years the number of thyroid cancer cases has increased 144% from 1709 to 4172 cases per year. Thyroid cancer is three times more common in females than males. 40% of thyroid cancers are diagnosed in Canadians under 45 years of age. Some of the apparent increase in incidence is likely due to improved and more widely available diagnostic techniques.

TITRE: Le cancer au Canada : Série de fiches d'information n° 1 - Le cancer de la thyroïde au Canada. RÉSUMÉ: Au Canada, l'incidence du cancer de la thyroïde croît plus rapidement que celle de tout autre cancer, mais le taux de mortalité est demeuré faible et stable. Au cours des dix dernières années, le nombre de cas de cancer de la thyroïde a augmenté de 144 %, passant de 1 709 à 4 172 cas par an. Le cancer de la thyroïde est trois fois plus fréquent chez la femme que chez l'homme. Quarante pour cent des cancers de la thyroïde ont été diagnostiqués chez les moins de 45 ans. Une partie de cette hausse apparente de l'incidence s'expliquerait par des techniques de diagnostic plus efficaces et plus largement accessibles.

Cancer incidence, mortality and survival trends in Canada, 1970-2007.

INTRODUCTION: Monitoring cancer trends can help evaluate progress in cancer control while reinforcing prevention activities. This analysis examines long-term trends for selected cancers in Canada using data from national databases. METHODS: Annual changes in trends for age-standardized incidence and mortality rates between 1970 and 2007 were examined by sex for 1) all cancers combined, 2) the four most common cancers (prostate, breast, lung, colorectal) and 3) cancers that demonstrate the most recent notable changes in trend. Five-year relative survival for 1992-2007 was also calculated. RESULTS: Incidence rates for all primary cancer cases combined increased 0.9% per year in males and 0.8% per year in females over the study period, with varying degrees of increase for melanoma, thyroid, liver, prostate, kidney, colorectal, lung, breast, and bladder cancers and decrease for larynx, oral, stomach and cervical cancers. Mortality rates were characterized by significant declines for all cancers combined and for most cancers examined except for melanoma and female lung cancer. The largest improvements in cancer survival were for prostate, liver, colorectal and kidney cancers. While the overall trends in mortality rates and survival point to notable successes in cancer control, the increasing trend in incidence rates for some cancers emphasize the need for continued efforts in prevention.

Canadian trends in liver cancer: a brief clinical and epidemiologic overview.

Although primary liver cancer is rare, its incidence rate has been rising quickly in Canada, more than tripling since the early 1980s. This cancer is more common in men than women, and the age-specific incidence rates in men have been increasing significantly in all age groups from 40 years of age onward. The death rate has followed a similar upward trajectory, in part because of the low 5-year survival rate of 18% in both sexes. Infection with the hepatitis B or C virus continues to be the most common risk factor, but other factors may also play a role. Risk reduction strategies, such as viral hepatitis screening, have been recommended in other countries and warrant consideration in Canada as part of a coordinated strategy of disease prevention and control.

Mortality and cancer incidence in a nickel cohort.

BACKGROUND: Previous studies of nickel workers have primarily noted significant early increases in lung and nasal cancers and for various types of accidents. AIMS: To examine cancer incidence and mortality, concurrently, for a cohort of male nickel workers at a major nickel and copper producer in Sudbury, Ontario, Canada. METHODS: From January 1964 to December 2001, nominal roll and work history information were linked to Ontario health data and mortality and cancer incidence were compared to the Ontario population. RESULTS: There were 1984 (19%) deaths and 1127 (11%) incident cancers (n = 10,253). Significant elevations in mortality were observed for accidents, poisoning and violence; for possibly job-related accidents among those with <15 years since first hire [standardized mortality ratio (SMR) = 133, 95% CI: 111-158; SMR = 241, 95% CI: 159-351, respectively] and for accidents in those with > or =15 years since first hire (SMR = 123, 95% CI: 104-144). Significant elevations were also observed for accidents, poisoning and violence for those with 6 months to 14 years work experience and for lung cancer incidence and mortality for those with 15-29 years work experience (SMR = 128, 95% CI: 107-153). Incident lung cancers were significantly elevated for those hired in the 1940s and 1960s. CONCLUSIONS: Significant lung cancer mortality and incidence elevations were observed for the cohort and underground workers with increased time since first hire, for those hired during early periods of operation and for those with longer durations of employment. Further aetiological study is required as occupational aetiology could not be ascertained.

Trends in childhood injury mortality in Canada, 1979-2002.

OBJECTIVE: To examine national trends in mortality rates for injuries among Canadian children younger than 15 years in 1979-2002. METHODS: Data on injury deaths were obtained from the Canadian Vital Statistics system at Statistics Canada. Injuries were classified using the codes for external cause of injury and poisoning (E-codes) by intent and by mechanism. Mortality rates were age adjusted to the 1990 world standard population. Negative binomial regression was used to estimate the secular trends. RESULTS: Annual mortality rates for total and unintentional injuries declined substantially (from 23.8 and 21.7 in 1979 to 7.2 and 5.8 in 2002, respectively), whereas suicide deaths among children aged 10-14 showed an increasing trend. All Canadian provinces and territories showed a decreasing trend in mortality rates of total injuries. Motor vehicle related injuries were the most common cause of injury deaths (accounted for an average of 36.4% of total injury deaths), followed by suffocation (14.3%), drowning (13.5%), and burning (11.1%); however, suffocation was the leading cause for infants. The number of potential years of life lost due to injury before age 75 decreased from 89 343 in 1979 to 27 948 in 2002 for children aged 0-14 years. CONCLUSIONS: During the period 1979-2002, there were dramatic decreases in childhood mortality for total injuries and unintentional injuries as well as various degrees of reduction for all causes of injury except suffocation in children aged 10-14 years and drowning in infants. The reason for the reduction in injury mortality might be multifactoral.

Survival patterns for the top four cancers in Canada: the effects of age, region and period.

This study examined the variations in survival rates (1989-1991) and the trends (1969-1991), by sex, age and province, for patients diagnosed with breast, colorectal, lung or prostate cancer in Canada and compared the Canadian rates with those of nine American SEER registries. Five-year age-standardized relative survival rates (ASRs) were calculated, and the trends were estimated from variance-weighted linear regression of the ASRs for five periods of diagnosis (1969-1973, 1974-1978, 1979-1983, 1984-1988 and 1989-1991). In 1989-1991, the ASR varied among provinces for each cancer except female colorectal cancer. The lowest survival rates were observed in the youngest patients (15-44) for breast and prostate cancers, and in the oldest patients (75-99) of both sexes for lung and colorectal cancers. Over the five periods, a major trend toward improved survival was observed for breast, prostate and colorectal cancers (P<0.008), whereas no changes were seen for lung cancer. The ASRs in the western region were higher than in the Atlantic region over time (P<0.02) for each cancer. From the third period onward, the ASRs for Canadian patients with lung cancer were similar to those for the US patients and lower than for Canadian patients with breast, prostate or colorectal cancer. The observed increases in ASR for breast and prostate cancer are likely due to the increased use of screenings and the improved treatment modalities.

Survival of women with breast cancer in Ottawa, Canada: variation with age, stage, histology, grade and treatment.

This study examined the 5-year survival of 2192 breast cancer women diagnosed between 1994 and 1997 in Ottawa, Canada, by age, TNM stage, histology, grade and treatment, including assessment of the independent value of variables in defining prognosis. Our results showed that age, stage, treatment and grade significantly influenced outcome regardless of the confounding factors considered, with histology failing to achieve significant independent prognostic information. The survival rates were highest at ages 50-69 years for stage I and at ages 40-49 years for stages II-IV. The rates were lowest at ages or=70 years for stages III-IV. The differences in survival between grade 1 and grade 3 were 9% in stage I and 20% in stage II. The treatment leading to the best survival was surgery plus radiation for stages I-II and surgery combined with chemotherapy for stages III-IV. Lobular carcinoma had a better prognosis than ductal carcinoma; this can be explained by more grade 1 and less grade 3 cases in lobular carcinoma. The worse prognosis for young patients than other ages can be explained by their higher proportion of poorly differentiated cancers. Stage I patients aged 50-69 years having the best survival is likely due to the earlier diagnosis achieved through screening.

Active and passive smoking and the risk of stomach cancer, by subsite, in Canada.

This study assessed the influence of active and passive smoking on the risk of stomach cancer by subsite. Mailed questionnaires were used to obtain information on 1171 newly diagnosed histologically confirmed stomach cancer cases and 2207 population controls between 1994 and 1997 in eight Canadian provinces. Data were collected on socio-economic status, lifestyle and passive smoking status. Odds ratios (OR) and 95% confidence intervals (95% CI) were derived by logistic regression. Compared with those who had never smoked, there was strongly increased risk for ex- and current smokers among subjects with cardial stomach cancer. For men with cardial cancer, the adjusted ORs were 1.9 (95% CI 1.2-3.0) and 2.6 (95% CI 1.6-4.3) for ex-smokers and current smokers, respectively, with a similar pattern among women. Among men, the adjusted ORs were lower for subsites of stomach cancer other than cardia. These findings suggest that active and passive smoking may play an important role in the development of cardial stomach cancer.

Increasing thyroid cancer incidence in Canada, 1970-1996: time trends and age-period-cohort effects.

We examined time trends in thyroid cancer incidence in Canada by age, time period and birth cohort between 1970 and 1996. Age-specific incidence rates by time period and birth cohort were calculated and age-period-cohort modelling used to estimate effects underlying the observed trends. Overall age-adjusted incidence rates of thyroid cancer doubled, from 3.3 and 1.1 per 100 000 in 1970-72 to 6.8 and 2.2 per 100 000 in 1994-96, among females and males respectively. Almost all the increase between 1970-72 and 1994-96 was due to papillary carcinoma of the thyroid. Age, birth cohort and period effects significantly improved the fit of the model for females, while age and birth cohort effects were significant determinants of the incidence among males. There were significant differences in the patterns/curvature for age, period and birth cohort effects between women and men. Our results suggest that the increases in thyroid cancer incidence in Canada may be associated with more intensive diagnostic activities and change in radiation exposure in childhood and adolescence. Temporal changes in reproductive factors among young women may explain some of the gender differences observed.

Socioeconomic status and lung cancer risk in Canada.

BACKGROUND: Several epidemiological studies have found that lung cancer is inversely related to socioeconomic status (SES) and suggest it as a possible risk factor for lung cancer. This study examines SES and lung cancer risk in Canada. METHODS: Mailed questionnaires with telephone follow-up were used to obtain data on 3280 newly diagnosed, histologically confirmed lung cancer cases and 5073 population controls, between 1994 and 1997, in eight Canadian provinces. Measurement included information on SES, smoking habits, alcohol use, diet, residential and occupational histories and both residential and occupational exposure to environmental tobacco smoke (ETS). Odds ratios (OR) and 95% CI were derived from unconditional logistic regression analysis. RESULTS: Compared with high income adequacy, an increased risk was found among low income males and females, with adjusted OR of 1.7 (95% CI : 1.3-2.2) and 1.5 (95% CI : 1.1-2.0), respectively. Compared with < or = 8 years of education, the adjusted OR were 0.6 (95% CI : 0.5-0.7) and 0.6 (95% CI : 0.5-0.8) for > or = 14 years education among males and females, respectively. Lung cancer risk was significantly increased for males of some social classes. The population attributable risk for income adequacy, education and social class was 24%, 25% and 21% among males, respectively, and 14% and 19% for income adequacy and education among females, respectively, in this Canadian population. CONCLUSIONS: A statistically significant association between income adequacy, education social class and lung cancer risk was found.

Incidence of second primary breast cancer among women with a first primary in Manitoba, Canada.

Second primary breast cancer is of importance because of the increasing incidence of first primary breast cancer and improved survival. There is lack of information on the disease in Canada. We studied 14,220 women with a first primary breast cancer (invasive only) diagnosed during the period from 1970 to 1997, in Manitoba, Canada. A breast cancer was considered to be a second primary if it was an invasive lesion diagnosed at least six months after the diagnosis of an initial primary breast cancer. The incidence rate of second primary breast cancer was approximately six per 1,000 person-years, and the cumulative incidence during the 28-year study period was 14.3%. Average age at diagnosis of first primary breast cancer had increased significantly since 1970. The incidence was higher in 1975-1979, and there was no significant difference among other study periods after adjustment for the age at diagnosis of first primary breast cancer. Standardized incidence ratios showed no significant difference among six age groups after adjusting for calendar year. However, women with a first primary breast cancer had an increased risk of developing a second primary breast cancer compared with the risk of developing a first primary breast cancer among the general female population. The SIR was markedly greater among women who had a first primary breast cancer before the age of 40 years, and decreased significantly with increasing age at diagnosis of first primary breast cancer. The data provide epidemiological information on second primary breast cancer risk for the general female population in Manitoba, Canada.

Cervical cancer in Canada: changing patterns in incidence and mortality.

Data on incidence of cervical cancer by histologic subtype and mortality for the Canadian provinces of Ontario, Saskatchewan, and British Columbia were used to examine time trends by age, calender period, and birth cohort. Age-adjusted incidence rate of squamous cell carcinoma of the cervix decreased from 11.1 per 100,000 women in 1970-72 to 5.3 in 1994-96, while the rate for cervical adenocarcinoma increased from 1.1 per 100,000 women to 1.5 over the same period. Age-adjusted mortality rate declined from 7.9 per 100,000 women in 1953-55 to 1.9 in 1995-97. The patterns in age-specific mortality rates in 1953-72 were different from those in 1973-97; younger women experienced larger reductions in mortality during the earlier period while older women benefited to a greater extent during the latter period. Age-period-cohort modeling showed that cohort effects were responsible for the decreasing trends in incidence of squamous cell carcinoma of the cervix and increasing trends in adenocarcinoma, and both period and cohort effects account for the observed trends in mortality. The results suggest that Pap smear screening has played a significant role in the reduction in squamous cell cervical carcinoma. The causes for the increase in cervical adenocarcinoma are unclear.

Orius software: calculation of rates and epidemiologic indicators, and preparation of graphical output.

Orius software produces disease surveillance statistics, including output for the Health Canada Web site "Cancer Statistics Online" and on-demand statistics at the Web site for the North American Association of Central Cancer Registries. It allows flexibility in accessing data; storing, modifying and customizing requests; and producing statistical results and graphical output. Results include age-standardized or age-sex-standardized rates, standardized incidence/mortality ratios (observed-to-expected ratios) in which one area is optionally selected as the reference, potential years of life lost, average annual percent change, Mantel-Haenszel and maximum likelihood rate ratios, and the comparative incidence figure.

Clues to the aetiological heterogeneity of testicular seminomas and non-seminomas: time trends and age-period-cohort effects.

BACKGROUND: Most previous epidemiological studies have treated testicular cancer as a single entity. However, some investigators suggest that testicular seminomas and non-seminomas may have different risk profiles. We examine the time trends in incidence of the two main histological types separately. METHODS: From 1970 through 1995, 7296 cases of testicular cancer were registered in the Canadian provinces of Ontario, Saskatchewan and British Columbia. In addition to analyses of the secular trends by age group and birth cohort, an age-period-cohort (APC) model with standard Poisson assumptions was fitted to the data to assess the time effects. RESULTS: The age-adjusted incidence rate for seminomas increased by 53%, from 1.5 per 100 000 males in 1970-1971 to 2.3 per 100 000 males in 1994-1995. Non-seminomas increased by 91%, from 1.1 to 2.1 per 100 000 males over the same period. Non-seminomas were more frequent at young ages whereas seminomas dominated in older ages. In contrast to seminomas, non-seminomas occurred predominantly among adolescent men (15-19 years), with a fourfold increase between 1970-1971 and 1994-1995. Age-period-cohort modelling showed that the increase in the risk of both seminomas and non-seminomas followed a birth cohort pattern, but with differences in birth cohorts in addition to significantly distinct age patterns. CONCLUSIONS: Our findings support the hypothesis postulating aetiological heterogeneity in the development of seminomas and non-seminomas. We suggest that epidemiological studies of testicular cancer treat seminomas and non-seminomas separately.

Methodological issues in the development of the Canadian Cancer Incidence Atlas.

The Canadian Cancer Incidence Atlas is among recent national atlases using incidence rather than mortality data. Methods used to assess the significance and spatial correlation of the age-standardized rates (ASIRs) for the 290 census divisions are described. The expected number of cases by area was used to determine cancer sites with sufficient cases to be mapped. ASIR significance was assessed using a simulation based on a Poisson distribution. The consistency of the observed case distributions with the Poisson distribution was examined. The bootstrap confidence interval (CI) for the ASIR developed by Swift was used in the atlas. Spatial correlation was assessed with Moran's I/I(max) and the significance determined by a simulation in order to allow for area population variation. Data quality indicators typically used for cancer registries were presented, supplemented by a registry questionnaire.

Time trends and sex patterns in Hodgkin's disease incidence in Canada, 1970-1995.

PURPOSE: To examine time trends and sex patterns in Hodgkin's disease incidence in Canada, from 1970 through 1995. METHOD: In addition to analyses of the secular trends and sex ratio in incidence rates, age-period-cohort models were fitted to estimate the effects on the trends. Age-specific male/female incidence rate ratios were examined for the disease and for its two major histologic subtypes. RESULTS: The overall age-adjusted incidence rate of Hodgkin's disease decreased significantly in males (3.5 per 100,000 in 1970-71 to 2.8 in 1994-95) but only slightly in females (2.4 per 100,000 to 2.3). There was a significant increase in the incidence among females aged 10-29 and among males aged 10-24, but a dramatic decrease among older ages. Age-period-cohort modelling showed that birth cohort and period effects were responsible for the observed trends in males and females, respectively. CONCLUSION: The risk factors responsible for Hodgkin's disease are different in females and males. Reproductive factors are likely to be associated with the occurrence of the disease in young women.

Epidemiology of contralateral breast cancer.

Two to 11% of women diagnosed with breast cancer will develop contralateral breast cancer in their lifetime. Women with a first primary are at a 2-6-fold increased risk of developing contralateral breast cancer compared with the risk in the general population of women developing a first primary cancer. The incidence rate of contralateral breast cancer varies from four to eight per 1000 person-years. To assess the risk factors associated with the development of contralateral breast cancer among women with a first primary breast cancer, the epidemiological literature concerning these factors was reviewed and summarized. Studies have shown that a family history of breast cancer, an early age at initial diagnosis, and a lobular histology of the first primary breast cancer increase the risk of developing contralateral breast cancer. Although chemotherapy and tamoxifen therapy may reduce this risk, there are inconsistent results regarding the effects of radiotherapy and the effects of reproductive, environmental and other factors. Additional analytical studies addressing all potential risk factors associated with the development of contralateral breast cancer are necessary in view of the increasing incidence and survival of women with a first primary.