Screening Colonoscopy Reduces the Risk for Incident Late-Stage CRC in Average-Risk Persons

March 2013, Vol 4, No 3 - In the Literature

Evidence is lacking regarding the efficacy of colonoscopy screening in reducing the incidence of and death from colorectal cancer (CRC) in persons with average risk. By contrast, the evidence for the efficacy of sigmoidoscopy or fecal occult blood test (FOBT) has been established. Nevertheless, and despite the high cost of colonoscopy and the potential risks associated with this procedure, colonoscopy is rapidly replacing sigmoidoscopy and FOBT in the United States as the standard screening test for CRC. It is therefore important to better understand the ability of colonoscopy to diagnose incident CRC in low- or average-risk persons. Late diagnosis is associated with increased risk for death from this disease.

 the link between screening colonoscopy and the risk for incident late-stage CRC in persons at average risk for CRC (Doubeni CA, et al. Ann Intern Med. 2013;158:312-320). The study included a total of 1039 adults at average risk for CRC (aged 55-85 years) who were enrolled at a health plan for at least 5 years. Persons with a history of total colectomy, a history of inflammatory bowel disease, or a strong family history of CRC were excluded from the study.

Of the 1039 enrolled persons, 498 patients (24 were excluded from the final analysis) were diagnosed with incident primary late-stage CRC between 2006 and 2008; the control group included 541 persons with no CRC diagnosis (3 of them were excluded from the final analysis). Of the final 474 case patients, 38 had stage IIB tumor, 279 had stage III tumor, and 157 had stage IV cancer; of these, 251 were right colon cancer, 206 were left colon cancer, and 17 had no specific location. Of the case patients, 13 (2.8%) had undergone screening colonoscopy compared with 46 (9%) in the control group, which corresponds to an adjusted odds ratio (OR) of 0.29 (95% CI, 0.15-0.58) for any late-stage CRC, 0.36 (95% CI, 0.16-0.80) for right colon cancer, and 0.26 (95% CI, 0.06-1.11; P = .069) for left colon/rectal cancer. Furthermore, 92 (19.5%) case patients and 173 (34%) controls had screening sigmoidoscopy, which corresponds to an adjusted OR of 0.50 overall, 0.79 for late-stage right colon cancer, and 0.26 for left colon cancer.

These results indicate that colonoscopy screening is associated with a reduced risk of diagnosis of incident late-stage CRC, including right-sided colon cancer, in average-risk persons. A significantly reduced risk for late-stage left CRC is also seen with sigmoidoscopy, but not for late-stage right colon cancer.

This study confirms that the use of screening colonoscopy is associated with a significant reduction in the risk of diagnosis of late-stage incident CRC.