TEMPORAL PATTERNS IN COLORECTAL-CANCER INCIDENCE, SURVIVAL, AND MORTALITY FROM 1950 THROUGH 1990

Background: Colorectal cancer mortality rates among U.S. white males r emained relatively constant from 1950 through 1984 but declined sharpl y from 1985 through 1990. Those for U.S. white females decreased consi stently from 1950 through 1984, with an acceleration of the decline fr om 1985 through 1990. Purpose: A study was planned to investigate patt erns in incidence, survival, and mortality rates over time in order to examine possible reasons for the gender difference in mortality trend s and for the decrease in the slope of the mortality trends for both m ales and females in the late 1980s. Methods: Incidence and survival da ta from the Connecticut Cancer Registry were examined to investigate t he gender differences in mortality rates from 1950 through 1981. Incid ence and survival data from the Surveillance, Epidemiology, and End Re sults (SEER) Program were investigated to examine reasons for the abru pt downturn in mortality rates for both white males and white females beginning around 1985. Results: During the period 1950 through 1984, t he colorectal cancer incidence rates in Connecticut increased for male s and declined slightly for females. Survival rates were similar for b ath sexes, increasing on average over 1% per year for both females and males from 1950 through 1984. Examination of SEER data from 1975 thro ugh 1990 revealed that for both males and females there were 1) declin es in overall incidence and mortality rates beginning in the mid-1980s , 2) steady declines in distant disease incidence rates since 1975, 3) increases in regional disease incidence rates until the early 1980s f ollowed by declines in the late 1980s, and 4) increases in local disea se incidence rates until the mid-1980s followed by declines in the lat e 1980s. Age-period-cohort analyses of mortality rates indicated a sta tistically significant moderation of colorectal cancer risk with both advancing birth cohorts and recent calendar periods. Conclusions: The gender differences in colorectal cancer mortality rate trends observed from 1950 through 1984 are due to differences in incidence rate trend s between males and females. Declining colorectal mortality rates in t he late 1980s for males and females appear to reflect improved early d etection. The peaking and subsequent decline of stage-specific inciden ce rates at later years for successively lower stage indicate sequenti al stage shifts as cancers are detected increasingly earlier over time . The increased use of sigmoidoscopy and fecal occult blood tests (tri ggering colonoscopy) appears to have played an important role in reduc ing colorectal cancer mortality. Improvements in birth cohort trends i n risk for colorectal cancer for each sex suggest that lifestyle chang es may have also contributed to the steady reductions in colorectal ca ncer mortality.