Increasing crude and adjusted mortality rates for colorectal cancer in a developing South American country

Colorectal cancer (CRC) is a major cause of cancer death worldwide. We examined temporal trends in death rates from colorectal cancer in Chile from 1983 to 2008.

We analysed the mortality database in Chile from 1983 to 2008. Cases were selected using ICD-9/10 codes. We calculated mortality rates per 100,000 inhabitants according to sex, age group and type of cancer - colon (CC) or rectal (RC). The rates were adjusted by a direct method using the WHO-2000 standard population. Time trends were assessed with Prais-Winsten regression models.

There were 26,250 deaths from CRC (75.7% for CC). There was a higher frequency of deaths from CC (57.6%) in women than in men, who had a higher frequency of deaths from RC (51.3%). The crude CC mortality rate increased by 116% (from 3.6 to 7.8), while the overall RC rate increased by 71% (from 1.4 to 2.4). After adjusting for age, a significant increase in mortality rate was found for CC (coefficient 0.09, 95% CI 0.08-0.11, P < 0.001) and RC (coefficient 0.02, 95% CI 0.009-0.04, P = 0.002) in men. In women, this increase was significant for CC (coefficient 0.03, 95% CI 0.005-0.05; P = 0.02), but not for RC (coefficient -0.007, 95% CI -0.02 to 0.005, P = 0.23).

The crude mortality rate from CRC has doubled in Chile in this period. After adjustment of mortality rates, it appears that much of this increase is due to the aging population. However, part of this increase could be explained by other factors.