Changes in early- and late-stage colorectal cancer incidence during the era of screening: 1976-2009.

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1522 Background: Ideally, screening detects cancer at a more curable stage, and as a result decreases the incidence of subsequent diagnosis at a late stage. Whereas breast cancer screening is suggested to have led to a substantial increase in the number of early-stage cancers diagnosed in the United States with only marginal reductions in the number of late stage cancers, the impact of colorectal cancer screening on cancer incidence is unknown. Methods: Colorectal cancer incidence data spanning over three decades, 1976—2009, were collected from the Surveillance, Epidemiology, and End Result (SEER) database. Screening utilization data spanning 1986—2010 were collected from the National Health Survey (NHS) progress reports. We examined trends in the incidence of early-stage (in situ, local) and late-stage (regional, distant) colorectal cancer among adults 50 years or older. Results: Over the past three decades, the incidence of late-stage colorectal cancer decreased significantly, from 118 to 74 cases per 100,000 people—a 37% decrease. The incidence of early-stage colorectal cancer also decreased, from 77 to 67 cases per 100,000 people. There was also an associated increase in the utilization rates of screening colonoscopy. From 1987 to 2010—the years for which NHS data were available—the percentage of adults 50 and older who received screening colonoscopy rose from 27% to 63%. After adjusting for trends in cancer incidence in non-screened populations, we estimated that colorectal screening was associated with a reduction of approximately 550,000 cases of colorectal cancer over the past three decades in the United States. Using the most conservative assumption of constant cancer incidence during the past three decades, 235,000 cases of colorectal cancer were prevented. Conclusions: There has been a significant decline in both early and late stage colorectal cancer diagnoses, during a time of increasing rates of increased screening.