Several previous studies have found that females and older individuals are at greater risk of having incomplete flexible sigmoidoscopy.
However, no prior study has reported the subsequent risk of colorectal cancer following incomplete sigmoidoscopy.
Dr Doria-Rose and colleagues used data from 55,791 individuals screened as part of the Colon Cancer Prevention programme of Northern California.
The investigators evaluated the likelihood of having an inadequate examination of more than 40 cm, by age and sex.
The investigative team estimated the risk of distal colorectal cancer according to depth of sigmoidoscope insertion at the baseline screening examination.
Multivariate estimation of risks was performed using Poisson regression.
The team found that older individuals of over 80 years had a relative risk of 3 of having an inadequate examination compared with 50 to 59 years.
|Colorectal cancer risk was 3-fold if the baseline sigmoidoscopy did not reach a 40 cm depth|
The investigators also noted that females were at a much greater risk, with a relative risk of 2.
The team observed that these associations were attenuated but remained strong if Poisson models were further adjusted for examination limitations.
The examination limitations applied by the team for testing these associations included pain, stool, and angulation.
The investigators reported a 3-fold increase in the risk of distal colorectal cancer if the baseline sigmoidoscopy did not reach a depth of at least 40 cm.
A smaller increase in risk was observed for examinations that reached 40 to 59 cm.
Dr Doria-Rose's team commented, “Older individuals and women are at an increased risk of having inadequate sigmoidoscopy.”
“Because inadequate sigmoidoscopy results in an increased risk of subsequent colorectal cancer, physicians should consider steps to maximise the depth of insertion of the sigmoidoscope.”
“Failing this, physicians should consider an alternative screening test.”