CORRESPONDENCE

RESPONSE: Re: Colorectal Cancer Screening: Sifting Through the Evidence

Bernard Levin

Correspondence to: Bernard Levin, M.D., M. D. Anderson Cancer Center, Houston, TX 77030 (e-mail: blevin{at}notes.mdacc.tmc.edu).

Dr. Atkins is correct in observing that there is no statistically significant difference in all-cause mortality in the screening and control groups of the Minnesota trial. However, all-cause mortality was not the end point of interest in this trial, and screening trials cannot reasonably address such an end point. The variability present in all-cause mortality is so great that it dominates even substantial differences in disease-specific mortality. Evidence of this is that the 95% confidence intervals for all-cause mortality in Table 1 of Mandel et al. (1) are far too wide to be able to detect a difference on the order of 4.6 deaths per 1000. Detecting such a difference in all-cause mortality with 90% power would require a trial with at least 500 000 participants.

There may well be screening interventions that cause death, either directly or indirectly, but this possibility has not been demonstrated for annual or biennial fecal occult blood testing. Therefore, it is appropriate to view such screening as saving lives, and it is reasonable to estimate this savings at 4.6 per 1000 screened.

REFERENCES

1 Mandel JS, Church TR, Ederer F, Bond JH. Colorectal cancer mortality: effectiveness of biennial screening for fecal occult blood. J Natl Cancer Inst 1999;91:434-7.[Abstract/Free Full Text]



             
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