The International Agency for Research on Cancer has coordinated a worldwide study of the incidence of cancer in childhood. Contributors from over 50 countries have provided data. This paper presents a summary of some of the major results. The incidence rates and relative frequencies of childhood cancers are described according to 12 diagnostic groups, defined mainly in terms of tumour morphology. Variations in the risk of those tumours between different countries and different ethnic groups provide important information on the relative importance of environmental and genetic factors in their aetiology.
Lung cancer rates have peaked among men in many areas of the world, but rates among women continue to rise. Most lung cancers are squamous cell carcinoma, small cell carcinoma, or adenocarcinoma; trends vary according to type. We compiled populationbased morphology-specific incidence data from registries contributing to the International Agency for Research on Cancer (IARC) databases. Unspecified cancers and carcinomas were reallocated based on a registry, time period, sex and age group-specific basis. Where available, data from several registries within a country were pooled for analysis. Rates per 100,000 person-years for 1980-1982 to 1995-1997 were age-adjusted by the direct method using the world standard. Squamous cell carcinoma rates among males declined 30% or more in North America and some European countries while changing less dramatically in other areas; small cell carcinoma rates decreased less rapidly. Squamous and small cell carcinoma rates among females generally rose, with the increases especially pronounced in the Netherlands and Norway. In contrast, adenocarcinoma rates rose among males and females in virtually all areas, with the increases among males exceeding 50% in many areas of Europe; among females, rates also rose rapidly and more than doubled in Norway, Italy and France. Rates of all lung cancer types among women and adenocarcinoma among men continue to rise despite declining cigarette use in many Western countries and shifts to filtered/low-tar cigarettes. Renewed efforts toward cessation and prevention are mandatory to curb the prevalence of cigarette smoking and to reduce lung cancer rates eventually. ' 2005 Wiley-Liss, Inc.Key words: lung cancer incidence; histology; trends There have been epidemics of lung cancer as incidence and mortality rates rose rapidly during the 20th century, especially among men and in the industrialized countries. 1,2 Among men, rates in the United States, Canada, England, Denmark and Australia have peaked, but they continue to rise in Spain, China and Japan. 1 Among women, rates have been considerably lower, increases started later and rates in most areas have not yet peaked. During 2000, an estimated 1.2 million cases were diagnosed, and 1.1 million deaths were attributed to lung cancer. Lung cancer may appear as squamous cell carcinoma, small cell carcinoma, adenocarcinoma, large cell carcinoma and a variety of other less frequent types. 3 The patterns and trends in incidence have varied by type, 4,5 related to differences in smoking patterns and exposures to other lung carcinogens. 1,6 The availability of populationbased histologic-specific incidence data from a number of registries contributing to the International Agency for Research on Cancer (IARC) databases 7 allows us to investigate the patterns in a number of geographic areas in a comprehensive fashion. Material and methodsPopulation-based cancer incidence data have been collected by many registries around the world for a number of years, and the IARC has compiled and published the data in the s...
The numbers of new cancer cases in 16 common sites occurring in 1980 have been estimated for 24 areas of the world for which the United Nations produces population estimates. For the world as a whole, the total number of new cases was 6.35 million, almost exactly evenly divided between the developed and developing countries. In males, the most important sites were lung, stomach, colon/rectum, mouth/pharynx, prostate and oesophagus, and in females breast, cervix, colon/rectum, stomach, corpus uteri and lung. When the two sexes are combined, stomach cancer emerges as the most common cancer in 1980 (669,400 new cases per year), but this estimate is only slightly greater than that of lung cancer (660,500 new cases), and comparisons with earlier estimates for 1975 suggest that, with declining incidence rates for stomach cancer and the continuing rise for lung cancer, the latter would become the most common cancer in the world by the end of 1981. The implications for cancer control in the developed and developing countries of the world are discussed.
This chapter summarises the results of the preceding sections, which estimate the fraction of cancers occurring in the UK in 2010 that can be attributed to sub-optimal, past exposures of 14 lifestyle and environmental risk factors. For each of 18 cancer types, we present the percentage of cases attributable to one or all of the risk factors considered (tobacco, alcohol, four elements of diet (consumption of meat, fruit and vegetables, fibre, and salt), overweight, lack of physical exercise, occupation, infections, radiation (ionising and solar), use of hormones, and reproductive history (breast feeding)).Exposure to less than optimum levels of the 14 factors was responsible for 42.7% of cancers in the UK in 2010 (45.3% in men, 40.1% in women) – a total of about 134 000 cases.Tobacco smoking is by far the most important risk factor for cancer in the UK, responsible for 60 000 cases (19.4% of all new cancer cases) in 2010. The relative importance of other exposures differs by sex. In men, deficient intake of fruits and vegetables (6.1%), occupational exposures (4.9%) and alcohol consumption (4.6%) are next in importance, while in women, it is overweight and obesity (because of the effect on breast cancer) – responsible for 6.9% of cancers, followed by infectious agents (3.7%).Population-attributable fractions provide a valuable quantitative appraisal of the impact of different factors in cancer causation, and are thus helpful in prioritising cancer control strategies. However, quantifying the likely impact of preventive interventions requires rather complex scenario modelling, including specification of realistically achievable population distributions of risk factors, and the timescale of change, as well as the latent periods between exposure and outcome, and the rate of change following modification in exposure level.
BackgroundChanging population-level exposure to modifiable risk factors is a key driver of changing cancer incidence. Understanding these changes is therefore vital when prioritising risk-reduction policies, in order to have the biggest impact on reducing cancer incidence. UK figures on the number of risk factor-attributable cancers are updated here to reflect changing behaviour as assessed in representative national surveys, and new epidemiological evidence. Figures are also presented by UK constituent country because prevalence of risk factor exposure varies between them.MethodsPopulation attributable fractions (PAFs) were calculated for combinations of risk factor and cancer type with sufficient/convincing evidence of a causal association. Relative risks (RRs) were drawn from meta-analyses of cohort studies where possible. Prevalence of exposure to risk factors was obtained from nationally representative population surveys. Cancer incidence data for 2015 were sourced from national data releases and, where needed, personal communications. PAF calculations were stratified by age, sex and risk factor exposure level and then combined to create summary PAFs by cancer type, sex and country.ResultsNearly four in ten (37.7%) cancer cases in 2015 in the UK were attributable to known risk factors. The proportion was around two percentage points higher in UK males (38.6%) than in UK females (36.8%). Comparing UK countries, the attributable proportion was highest in Scotland (41.5% for persons) and lowest in England (37.3% for persons). Tobacco smoking contributed by far the largest proportion of attributable cancer cases, followed by overweight/obesity, accounting for 15.1% and 6.3%, respectively, of all cases in the UK in 2015. For 10 cancer types, including two of the five most common cancer types in the UK (lung cancer and melanoma skin cancer), more than 70% of UK cancer cases were attributable to known risk factors.ConclusionTobacco and overweight/obesity remain the top contributors of attributable cancer cases. Tobacco smoking has the highest PAF because it greatly increases cancer risk and has a large number of cancer types associated with it. Overweight/obesity has the second-highest PAF because it affects a high proportion of the UK population and is also linked with many cancer types. Public health policy may seek to mitigate the level of harm associated with exposure or reduce exposure levels—both approaches may effectively impact cancer incidence. Differences in PAFs between countries and sexes are primarily due to varying prevalence of exposure to risk factors and varying proportions of specific cancer types. This variation in turn is affected by socio-demographic differences which drive differences in exposure to theoretically avoidable ‘lifestyle’ factors. PAFs at UK country level have not been available previously and they should be used by policymakers in devolved nations. PAFs are estimates based on the best available data, limitations in those data would generally bias toward underestimation of PAFs. R...
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