Colorectal Cancer In New Jersey
1979-1997

Discussion

Incidence Trends

The steady decline from 1985 to 1997 in annual age-adjusted colorectal cancer incidence rates among New Jersey residents mirrors the national trend.6 The reasons for this decline may include changes in diet such as increased consumption of fiber-containing foods and decreased intake of red meat and alcohol and increased physical activity. Higher use of nonsteroidal anti- inflamatory drugs such as aspirin or ibuprofen and more colorectal cancer screening with the removal of adenomatous polyps may also have contributed to the decline.3,6

The incidence trends of the three colorectal cancer subsites differed. Proximal colon cancer incidence rates increased between 1979 and 1985, then leveled off. Distal colon cancer incidence rates decreased steadily between 1979 and 1997 and rectal cancer incidence rates increased from 1979 to 1985, then steadily decreased. These subsite time trends were similar to those of the U.S. Overall, a steady decline in colorectal cancer incidence rates between 1985 and 1997 was observed in New Jersey.6

The percentage of colorectal cancers diagnosed in the earlier stages (in situ and local) between 1985 and 1997 increased overall and for the proximal and distal colon subsites.

Mortality Trends

The annual age-adjusted colorectal cancer death rates among New Jersey residents steadily declined between 1979 and 1997, similar to the national trend.6 The longer-term decline in mortality is probably related to improvements in colorectal cancer treatment and the increase in the proportion of colorectal cancers diagnosed in the early stages at which the chances for survival are greatest. The decline in the incidence rate of colorectal cancer also probably affected the mortality rates.

Incidence and Mortality Trends - Differences By Gender and Race

While the overall downward trend in colorectal cancer incidence and mortality is encouraging, not all groups of New Jersey residents shared in it. Although the incidence rate among black women declined overall from 1979 to 1997, the rate increased in three of the four most recent years (1994-1997). Black men's incidence rate also increased in three of the four most recent years and was higher in 1997 than in 1979 or in 1985. Before 1994, black men and women usually had lower annual incidence rates than their white counterparts, but this reversed after 1994.

Between 1979 and 1997, proximal colon cancer incidence rates increased in all the gender and race groups, particularly in black men and women. Distal colon cancer rates decreased at about the same rate among the four groups. Rectal cancer incidence rates decreased among white men and women, but increased among black men and women. Thus, the differences among the race and gender groups in the time trends in the incidence rates of colorectal cancer appear to be related to the different pattern of changes in the subsites, particularly in proximal colon and rectal cancer. The reasons may be related to differences between whites and blacks in the suspected risk factors, protective factors, and screening.

Each gender and race group showed an increase in the percentage of colorectal cancers diagnosed in the early stages; the increases were much larger for black men and women than white men and women. By 1997, the percentages of early stage diagnosis were similar among the four gender and race groups.

Between 1979 and 1997, black women consistently had higher annual mortality rates than white women and the gap widened between 1994 and 1997. Beginning in 1982, black men usually had higher annual mortality rates than white men and, like women, the gap widened between 1994 and 1997. Both black men and women's annual mortality rates declined overall between 1979 and 1997, but not as much or as steadily as white men and women's. Most notably, black men and women's mortality rates showed increases in the three most recent years. This happened despite the great improvement between 1985 and 1997 in the percent of incident colorectal cancers diagnosed in the early stages in black men and women. This is similar to the national trend6 and may reflect the differences in incidence and/or differences in treatment for colorectal cancer.

Screening

In recent years, less than half of the New Jersey population age 50 or over reported receiving colorectal screening at the recommended time intervals, similar to the proportion in the U.S. as a whole.6

Comparison of New Jersey and U.S. Rates

It is not known why the colorectal cancer incidence and mortality rates are higher in New Jersey than in the U.S. in recent years. A possible reason could be the higher prevalence of known or suspected risk factors. Higher rates of screening leading to the diagnosis of more colorectal cancers may also play a role. Poor access to state-of-the-art treatment, as well as higher incidence rates, could lead to overall higher mortality rates.6 New Jersey colorectal screening rates are similar to the those for the U.S.6, so screening probably does not explain the higher New Jersey incidence and mortality rates.

Conclusions

Although overall colorectal cancer incidence and mortality have steadily declined from 1979 to 1997, it remains a major cause of illness and death in New Jersey. At this time, increased attention to screening for colorectal cancer and promoting healthier lifestyles are the best methods for addressing this public health problem.


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