Screening option reduces bowel cancer risk for up to 17 years

Findings that a single flexible sigmoidoscopy exam in 55-64 years olds confers long-lasting protection against colorectal cancer are unlikely to change clinical practice in Australia, an expert says.

The UK Flexible Sigmoidoscopy Screening Trial (UKFSST) of over 170,000 people found the intervention reduced colorectal cancer incidence by 26% and colorectal cancer mortality by 30% for up to 17 years.

Commenting on the UK study, gastroenterologist Dr Cameron Bell told the limbic earlier findings from the UKFSST were well known. They were the catalyst for introducing flexible sigmoidoscopy to the NHS Bowel Cancer Screening Programme.

“We know it is a valid screening strategy that reduces mortality from and the incidence of colorectal cancer. The surprising thing here is that the effects extend out for another six years,” he said.

Dr Bell, senior staff specialist at the Royal North Shore Hospital and a member of the clinical advisory group for the National Bowel Cancer Screening Program (NBCSP), said flexible sigmoidoscopy was ineffective in protecting against right side cancers.

The study found the intervention reduced distal cancer incidence by 41% on an intention-to-treat analysis and by 56% on a per-protocol basis. There was no significant difference in proximal colon cancer between the intervention and control groups.

Dr Bell said no screening program was perfect and the most effective program was the one people were most likely to participate in.

“Australia has not developed an appetite for flexible sigmoidoscopy,” he said.

“Cancer Council Australia has done a lot of modeling on efficacy and cost effectiveness of various strategies and the draft Clinical practice guidelines for the prevention, early detection and management of colorectal cancer is out for public consultation at the moment.”

“There is nothing suggesting a move away from faecal occult blood testing.”

Dr Bell said a recent meta-analysis found long-term aspirin offered protection against proximal cancers. A combination of flexible sigmoidoscopy and aspirin may therefore provide another strategy for reducing the burden of colorectal cancer.

He said flexible sigmoidoscopy might also be an option for people who refused FOBT.

An accompanying editorial in The Lancet said the findings raised questions about the recommended intervals between colorectal cancer screenings.

“These findings suggest that the rate at which de-novo adenomas formed and transitioned to symptomatic colorectal cancer within 17 years was quite low. Current models of the natural history of adenoma should be reassessed to see if they are consistent with these long-term results,” the editorial said.

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