摘要：Objectives. We evaluated changes in colorectal cancer (CRC) incidence and mortality by anatomic site to assess the possible impact of CRC screening. Methods. Using data from 9 Surveillance, Epidemiology, and End Results cancer registries, we estimated trends in 1975–2007 CRC incidence and 1985–2007 incidence-based mortality. We evaluated trends separately for proximal and distal CRC, overall and by stage, tumor site, and race. Results. Between 1975 and 2007, 323 237 adults in the study area were diagnosed with CRC. For most tumor and population subgroups, incidence rates increased between 1975 and 1985 and subsequently declined markedly. Declines were most rapid between 1999 and 2007 and were greater for distal than proximal CRC. Declines in incidence were greater for White than Black adults and greatest for regional-stage disease. There was little difference in trends across subsites within the proximal and distal colorectum. Declines in incidence-based mortality mirrored those for incidence. Conclusions. Recent declines in CRC incidence and mortality are greater for distal than proximal CRC. Differing trends across populations may reflect variations in screening prevalence; distinct trends by tumor characteristics likely reflect differences in screening efficacy. Colorectal cancer (CRC) is the third most commonly diagnosed cancer and the second leading cause of cancer-related mortality in the United States. 1 Recent reports indicate a decline in the burden associated with CRC in the United States on the basis of changes in incidence 2–6 and mortality 2–4 rates over time. However, such patterns of decline have been shown to differ across population groups and according to tumor characteristics. 6–8 In particular, unequal declines in CRC mortality rates by race have resulted in increased racial disparities in CRC mortality, 7 and observed declines in incidence rates have been more pronounced with respect to distant stage than local stage disease. 6,8 The utilization of screening for CRC is likely a key contributing factor for these observed trends as well as for differences in trends across populations. 4,9–17 However, the benefits of certain CRC screening modalities have been reported to differ for tumors arising in different sites in the colon and rectum. 9–15,18,19 In particular, the sensitivity of fecal occult blood testing (FOBT) is higher for distal and rectal CRC than for CRC arising in the proximal colon, 19 sigmoidoscopy does not allow visualization of the proximal colon, and there is some suggestion that colonoscopy of the entire large bowel is more strongly associated with a reduction in risk of incidence and mortality for distal than for proximal CRC. 11,12,14 Thus, to the extent that screening is responsible for observed declines in CRC incidence and mortality, temporal trends in CRC may be expected to differ across populations and tumor subgroups. We have characterized temporal patterns of CRC incidence and incidence-based mortality (IBM) across anatomic locations and tumor stage and according to population characteristics, with the underlying goal of characterizing the impact that screening may have had on these rates.
