Spatial variation in stage distribution in colorectal cancer in the Netherlands

In the Netherlands the incidence of colorectal cancer has increased, mainly in the eastern part of the country. Patient delay due to unawareness or ignorance of symptoms and differences in use of diagnostic tools could have influence on the stage distribution. The aim of this study was to evaluate geographical differences in stage-specific incidence rates of colon and rectal cancer in the Netherlands.

Age-adjusted incidence rates for cancers of the colon and rectum diagnosed in 2001-2005 and registered in the Netherlands Cancer Registry were calculated for each municipality and stage. The incidence for each 500m by 500m grid was estimated as a weighted average of the incidence rates of the neighbouring municipalities. The incidence rates and the stage distribution are both presented as maps. Geographic variation in stage-specific incidence was evaluated using spatial scan statistic.

In both colon and rectal cancer, significant spatial variation in stage-specific incidences was found, except for colon cancer of stages III and IV. The regions with a higher stage-specific incidence were almost all in the south eastern part of the Netherlands, however, these differences were not seen in the stage distribution. There were no differences in stage distribution between large cities and the rest of the country.

These maps give insight into differences in stage-specific incidences of colon and rectal cancer in the Netherlands. Educational interventions to increase the awareness of symptoms of colorectal cancer may be especially useful for the population in regions with high incidence of advanced stages.