Academic journal article Bulletin of the World Health Organization

An Assessment of GLOBOCAN Methods for Deriving National Estimates of Cancer incidence/Evaluation Des Methodes GLOBOCAN Pour Etablir Des Estimations Nationales De I'incidence Du cancer/Una Evaluacion De Los Metodos GLOBOCAN Para Obtener Estimaciones Nacionales De la Incidencia De Cancer

Academic journal article Bulletin of the World Health Organization

An Assessment of GLOBOCAN Methods for Deriving National Estimates of Cancer incidence/Evaluation Des Methodes GLOBOCAN Pour Etablir Des Estimations Nationales De I'incidence Du cancer/Una Evaluacion De Los Metodos GLOBOCAN Para Obtener Estimaciones Nacionales De la Incidencia De Cancer

Article excerpt

Introduction

Cancer is among the most common causes of morbidity and mortality worldwide, with an estimated 14 million new cases and 8 million deaths in 2012, projected to rise by at least 70% by 2030. (1) Timely and accurate cancer statistics are crucial to identify priorities for cancer control strategies at the national level. Yet, only 34 of 194 World Health Organization (WHO) Member States presently report high-quality national mortality data, (2) while 68 countries provided high-quality incidence data for the last volume of Cancer incidence in five continents' As a result, many policy-makers rely on national cancer incidence and mortality estimates of variable precision to inform cancer control priorities.

GLOBOCAN, a project of the International Agency for Research on Cancer (LARC) provides estimates by cancer site and sex using the best available data in each country and several methods of estimation. (1) Producing high-quality estimates therefore requires a dual approach of improving the reported data (developing cancer registries and civil/vital registration systems) and a continual assessment of the validity of the estimation procedures to improve the methods used.

This study focuses on the validity of the methods used in GLOBOCAN to derive national cancer incidence estimates, based on a retrospective comparison of these estimates to the observed national data in a setting with high quality cancer registry data. Although we focused on the methods most commonly used in high-income countries, we also aimed at providing insights into the validity of the methods more broadly, including methods used more predominantly in low- and middle-income countries.

Methods

Recorded data

To validate the nine methods used in GLOBOCAN to estimate national incidence in 2012 (GLOBOCAN 2012), long-term national and regional incidence and mortality data as well as 5-year relative survival estimates are required. Of the few countries with such data available, we selected Norway because of the consistently high quality of its cancer registry data, available nationally and by region. Cancer reporting is a legal requirement in Norway and data linkage procedures with the cause of death registry further increase the completeness of the information. For the period 2001-2005, data completeness was estimated at 98.8%, while 93.8% of the cases had been verified by examining biopsy samples under a microscope. (4)

From the Nordic cancer database NORDCAN, we extracted Norwegian incidence and mortality data by region, year of diagnosis, cancer site, sex and 5-years age group (starting at 0-4 and ending at 85+) for the period 1983-2012. (5) We also extracted Norwegian 5-year relative survival proportions for each cancer site as well as incidence and mortality data from neighbouring countries Denmark, Finland, Iceland and Sweden. (5) As with GLOBOCAN 2012, national population data were obtained from the United Nations (6) while regional population data were extracted from NORDCAN. (5)

Cancer sites of the recorded cases and deaths were grouped by the codes in the International statistical classification of diseases and related health problems, 10th revision (ICD-10) to correspond to the sites used in GLOBOCAN. Unspecified neoplasms of the uterus (ICD-10 code C55) were reallocated to the cervix (C53) and corpus uteri (C54) according to the respective proportions of these two sites in the different datasets. (7)

We computed the number of cases by sex and cancer site in Norway in 2010 as the average of the recorded cancer cases between 2009 and 2011 to define a gold standard for comparisons. We then applied each of the nine methods used in GLOBOCAN 2012 to estimate the number of cancer cases in Norway in 2010, by sex and cancer site, and compared these estimates with the gold standard.

Estimation methods

The GLOBOCAN methods are summarized in Fig. …

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