Screening for Colorectal Cancer with Flexible Sigmoidoscopy: Is a 5-Yr Interval Appropriate? A Comparison of the Detection of Neoplasia 3 Yr versus 5 Yr After a Normal Examination

Carol A. Burke, M.D.; Kareem Elder, M.D.; Rocio Lopez, M.S.

Disclosures

Am J Gastroenterol. 2006;101(6):1329-1332. 

In This Article

Abstract and Background

Context: The recommended interval for colorectal cancer screening with flexible sigmoidoscopy (FS) was recently lengthened from 3 to 5 yr. Direct evidence supporting the longer interval is lacking. The appropriateness of the longer interval has been questioned.
Objective: To compare the incidence of neoplasia detected on FS in individuals who had undergone an FS either 3 yr or 5 yr after a normal examination.
Design, Settings, and Patients: Subjects were drawn from 5,359 individuals who underwent two FS examinations performed for colorectal cancer screening. Examinations were performed by gastroenterologists at a single academic medical center between 1987 and 2002. A total of 2,146 subjects with a normal baseline examination and a follow-up examination 3 and 5 yr later was included.
Main Outcome Measure: To compare the incidence of neoplasia, including advanced neoplasia, detected 3 yr versus 5 yr after a normal FS.
Results: 915 subjects underwent FS at 3 yr and 1,231 subjects at 5 yr after a normal examination. Neoplasia was detected in 3.2% of the 3-yr and 4.3% of the 5-yr subjects (p = 0.17). No significant differences were detected in the pathology, multiplicity, or size of neoplasms between the 3- and 5-yr groups. Advanced neoplasms occurred in 0.9% (including one adenocarcinoma) of subjects at 3 yr and 1.1% of subjects at 5 yr (p = 0.67).
Conclusions: Few individuals will develop rectosigmoid neoplasms 3 or 5 yr after a normal FS. The majority of neoplasms detected are low-risk lesions. A screening interval of 5 yr after a normal FS does not portend an increased risk of advanced neoplasms including cancer. This direct evidence supports the current recommendations of a 5-yr interval for colorectal cancer screening with FS.

Colorectal cancer remains the second leading cause of cancer deaths in the United States. Approximately 146,940 new cases of colorectal cancers were diagnosed in 2004, and 56,730 individuals are expected to die secondary to this disease.[1] Colorectal cancer screening is recommended by all major gastrointestinal societies as well as the United States Preventive Services Task Force.[2,3,4,5,6] Although colonoscopy is becoming the preferred screening modality, its cost, risk, and availability are deterrents to its widespread implementation. Therefore, other options including fecal occult blood testing, flexible sigmoidoscopy (FS), and air contrast barium enema are recommended as alternatives.

In 1997, many published guidelines lengthened the recommended interval for screening FS from 3 to 5 yr.[2,3,4] The majority of the evidence used to support the lengthened interval is based on case-controlled trials or cohort studies, which have found a mortality benefit from the use of FS up to 10 yr after the examination.[7,8,9,10,11,12,13] Direct evidence to support the longer interval is lacking. Recently a study published in JAMA by Schoen et al., called into question the appropriateness of a 5-yr delay between screening FS.[14] This concern was based on the finding that 3.1% of subjects had neoplasia and 0.8% harbored advanced neoplasia 3 yr after a negative baseline examination.

Our aim was to establish whether waiting for 5 yr rather than 3 yr after a normal screening FS would be associated with an increased risk of neoplasia including incident advanced neoplasms.

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