Time to benefit for colorectal cancer screening: survival meta-analysis of flexible sigmoidoscopy trials
BMJ 2015; 350 doi: https://doi.org/10.1136/bmj.h1662 (Published 16 April 2015) Cite this as: BMJ 2015;350:h1662
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Dear Editors
I commend Tang et al for their work looking at survival data of flexible sigmoidoscopy trials to determine minimum time to benefit for colorectal cancer screening.
I would like to ask a simple question, but it may perhaps be that elephant in the room.
The authors stated that:
We determined that it took 4.3 years (95% confidence interval 2.8 to 5.8) to prevent one colorectal cancer related death per 5000 people screened with flexible sigmoidoscopy (absolute risk reduction 0.0002, table 2⇓). Similarly, it took 9.4 years (95% confidence interval 7.6 to 11.3) to prevent one colorectal cancer related death per 1000 people screened with flexible sigmoidoscopy (absolute risk reduction 0.001).
Further down the paper, they acknowledged that complications of the procedures is a limitation of their study "that there is much uncertainty around the rates of serious complications from screening flexible sigmoidoscopy". Therefore the 9.4 years for ARR of 0.001 is death from colorectal cancer itself but does not take into account death occasioning from complication of screening flexible sigmoidoscopy. It would be speculative but not unreasonable to suggest that the time to achieve ARR of 0.001 for death related to CRC screening by flexible sigmoidoscopy will be closer to 10 years
In addition, they also admitted that:
" Our previous survival meta-analysis of the time to benefit for fecal occult blood testing suggested that it would take 10 years (95% confidence interval 6 to 16) to avoid one death from colorectal cancer per 1000 people screened.30 Our current study shows that the time to benefit with flexible sigmoidoscopy is similar to that for fecal occult blood testing. While fecal occult blood testing and flexible sigmoidoscopy may detect different types of lesions, positive results from either screening test leads to colonoscopy, suggesting that the time to benefit for colonoscopy may be approximately 10 years."
Granted that we may be looking at different population data in their meta analysis performed separately on CRC screening by fecal occult blood testing alone and flexible sigmoidoscopy alone, then my question naturally is:
"If the time to achieve ARR 0.001 for both fecal occult blood testing alone and flexible sigmoidoscopy alone to prevent CRC death is more or less similar, does the costs, the time, resource allocations and complication from implementation of a national flexible sigmoidoscopy justify the benefits?"
Competing interests: I have previously commented on a paper quoted by the NHS to support of a national colorectal screening program using flexible sigmoidoscopy http://www.bjs.co.uk/details/yourviews/2698271/Systematic-review-and-metaanalysis-of-the-evidence-for-flexible-sigmoidoscopy-as.html
Re: Time to benefit for colorectal cancer screening: survival meta-analysis of flexible sigmoidoscopy trials
Thank you for your comment, Dr. Goh. The question you pose is an interesting one. Given the wide confidence intervals around the rates of complications from both fecal occult blood testing (FOBT) and flexible sigmoidoscopy (FS), it is unclear whether harms are higher with FOBT or FS. It is clear, though, that CRC screening is underutilized in large segments of the population. Therefore, we support providing choices to patients and their providers regarding CRC screening when it is unclear which modality has the greatest benefits and the least harms.
Competing interests: No competing interests