An alphanumeric scoring system, shown below, is used to independently describe the availability of incidence and mortality data at the country level. The combined score is presented together with the estimates for each country, to provide a broad indication of the robustness of the estimation.

Incidence data

• A. High-quality* national data or high-quality regional data (coverage: > 50%)
• B. High-quality* regional data (coverage: 10–50%)
• B. High-quality* regional data (coverage: 10–50%)
• D. National data (rates).
• E. Regional data (rates).
• F. Frequency data.
• G. No data.

*Data included in Cancer Incidence in Five Continents (CI5), Volume IX^a and/or X^b.

^aCurado MP, Edwards B, Shin HR, Storm H, Ferlay J, Heanue M, et al., editors (2007). Cancer incidence in five continents, Vol. IX. IARC Scientific Publication No. 160. Lyon: International Agency for Research on Cancer.

^bForman D, Bray F, Brewster DH, Gombe Mbalawa C, Kohler B, Piñeros M, et al., editors (2013). Cancer incidence in five continents, Vol. X. IARC Scientific Publication No. 164. Lyon: International Agency for Research on Cancer.

Mortality data

National statistics are collated and made available by the World Health Organization for countries with vital registration systems.

• A. High-quality* complete vital registration data
• B. Medium-quality* complete vital registration data
• C. Low-quality* complete vital registration data
• D. Incomplete or sample vital registration data
• E. Data from other sources (cancer registries, verbal autopsy surveys, etc.)
• F. No data

*Criteria defined in: Mathers CD, Ma Fat D, Inoue M, Rao C, Lopez AD (2005). Counting the dead and what they died from: an assessment of the global status of cause of death data. Bulletin of the World Health Organization. 83(3):161–240.

The methods of estimation are country-specific, and the quality of each estimation depends on the quality and amount of the information available that each country.

In theory, there are as many methods as countries, and because of the variety and complexity of these methods, an overall quality score for the incidence and mortality estimates combined is almost impossible to determine.

Incidence

The methods used to estimate the sex- and age-specific incidence rates of cancer in a specific country fall into the following broad categories, in order of priority:

• Rates projected to 2012 (38 countries)
• Most recent rates available applied to the 2012 population (20 countries)
• Estimated from national mortality data by modelling, using incidence mortality ratios derived from data recorded by country-specific cancer registries (13 countries)
• Estimated from national mortality estimates by modelling, using incidence mortality ratios derived from data recorded by local cancer registries in neighbouring countries (9 European countries)
• Estimated from national mortality estimates using modelled survival (32 countries)
• Estimated as a weighted average of local rates (16 countries)
• Estimated using the data from one cancer registry covering part of the country, which are treated as representative of the countrywide profile (11 countries)
• Age/sex specific rates for all cancers combined were partitioned using data on the relative frequency of individual cancers, by age and sex (12 countries)
• The rates are those of neighbouring countries or registries in the same area (33 countries)

Mortality

Depending of the degree of detail and the accuracy of the national mortality data, one of the following six methods was used, in order of priority:

• Rates projected to 2012 (69 countries)
• Most recent rates available applied to the 2012 population (26 countries)
• Estimated as a weighted average of regional rates (1 country)
• Estimated from national incidence estimates by modelling, using country-specific survival (2 countries)
• Estimated from national incidence estimates by modelling, using country-specific survival (2 countries)
• The rates are those of neighbouring countries or registries in the same area (3 countries)

The sources and methods used to estimate the global incidence and mortality in 2012, in addition to a brief description of the key results by cancer site and in 20 large areas of the world, can be found in Ferlay et al. (2015)^a. A further assessment of the methods has also been described by Antoni et al. (2016)^b.

Prevalence

The sex- and cancer-specific 1-, 3-, and 5-year prevalence estimates for 2012 were computed by multiplying the corresponding estimates for 2008^c by the ratios of the estimated number of incident cases in 2012 in the adult population to the corresponding estimated number of cases for 2008.

References

^aFerlay J, Soerjomataram I, Dikshit R, Eser S, Mathers C, Rebelo M, et al. (2015). Cancer incidence and mortality worldwide: sources, methods and major patterns in GLOBOCAN 2012. Int J Cancer. 136(5):E359–86. PMID:25220842

^bAntoni S, Soerjomataram I, Møller B, Bray F, Ferlay J (2016). An assessment of GLOBOCAN methods for deriving national estimates of cancer incidence. Bulletin of the World Health Organization. 94:174–84. doi: http://dx.doi.org/10.2471/BLT.15.164384

^cBray F, Ren JS, Masuyer E, Ferlay J. Estimates of global cancer prevalence for 27 sites in the adult population in 2008. Int J Cancer. 2013 Mar 1;132(5):1133-45. doi: 10.1002/ijc.27711. Epub 2012 Jul 26.