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Previous Volume 356:1581-1583 April 12, 2007 Number 15 Next

	Since this article has no abstract, we have provided an extract of the first 100 words of the full text and any section headings.

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To the Editor: Chen et al. (Jan. 4 issue)¹ state that their five-gene prognostic signature in non–small-cell lung cancer (NSCLC) was validated three times. However, validations 1 and 3 changed the measurement method that was used to define the signature under validation. Correct validation of a signature requires a new series of patients, a consistent statistical method to define the signature, and the same measurement technique.² Validation 1 reused the original cohort and changed the statistical method. Further doubts arise from the investigators' use of a decision tree for this analysis.

Stefan Michiels, M.Sc.
Catherine Hill, Ph.D.
Institut Gustave Roussy
. . . [Full Text of this Article]

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