Purpose: This article reports the incidence rates of colon and rectal cancer in Denmark during 55 years of data registration and estimates the number of cases identified attributable to four modifiable risk factors and potentially preventable.
Methods: On the basis of reports in the nationwide, population-based, Danish Cancer Registry, we calculated age-standardized, period-specific, incidence rates and age and birth cohort-specific incidence rates. To calculate the population attributable risk, relative risk estimates were obtained from meta-analyses, case-control, and prospective cohort studies, combined with data from surveys of the consumption of alcohol, red meat, vegetables, and level of physical activity.
Results: For both genders, the incidence rate of colon cancer increased, whereas the incidence rate for rectal cancer decreased during the period 1943 to 1997. The decrease in the incidence rate of rectal cancer was observed for both genders, but the incidence rate among males was higher than that among females. The proportion of cases that could have been prevented if the Danish population had not been exposed to the four known risk factors varied from 0 to 15 percent for each of the four risk factors.
Conclusions: This study shows that the incidence rate of colon cancer has increased, whereas that of rectal cancer has decreased in Denmark during 55 years of observation. The potentially preventable proportions of incident cases are substantial but not as high as might have been expected.