[Incidence trends of colorectal cancer in urban Shanghai, 1973 - 2005].

OBJECTIVE

To explore the time trends of colorectal cancer incidence rates in urban Shanghai from 1973 to 2005.

METHODS

Data on the incidence rates of colorectal cancer were obtained from a population-based cancer registry in Shanghai. A total of 32 962 colon cancer patients and 24 662 rectal cancer patients were registered. Population estimation were based on periodic censuses, with age- and sex-specific annual estimates derived for the remaining years. The rates were adjusted to the world standard population by using the direct method. Annul percent changes (APCs) in rates were estimated by means of a linear regression of the logarithm of the respective rates on calendar, weighted by the number of incidence cases.

RESULTS

The incidence rates of colorectal cancer increased steadily during 1973 to 2005, the age-adjusted incidence rates of colon cancer increased from 6.09 and 5.70 to 14.70 and 14.35 per 100 000 in male and female respectively. The APCs were 3.03% (t = 14.77, P < 0.01) and 3.21% (t = 22.15, P < 0.01). The rates of rectal cancer increased from 7.68 and 6.51 to 11.45 and 8.28 per 100 000 in male and female respectively. The APCs were 1.34% (t = 7.28, P < 0.01) and 0.93% (t = 7.34, P < 0.01). The top APCs for colon and rectal cancer in female were 5.86% and 2.79% at age above 85 and in male those were 4.64% and 2.38% at age of 80-. The APCs of colon cancer were greater than those of rectal cancer at the groups above 45 years old. The average ages when diagnosed were delayed from 57 - 60 to 66 - 70 during these 33 years. The average diagnosed ages of colon cancer were later than those of rectal cancer slightly (from 2003 to 2005, the onset age of male colon cancer: 68.61 +/- 12.17, male rectal cancer: 66.81 +/- 12.62, t = 4.90, P < 0.01; female colon cancer: 69.20 +/- 12.13, female rectal cancer: 67.75 +/- 12.54, t = 3.81, P < 0.01).

CONCLUSION

The incidence rates of colorectal cancer increased steadily during 1973 to 2005, especially for colon cancer. Further research is needed to identify the causes resulting in these changes.