Published in:
01-10-2014 | Commentary
RETRACTED ARTICLE: The ‘obesity paradox’ and
survival after colorectal cancer: true or false?
Author:
Andrew G. Renehan
Published in:
Cancer Causes & Control
|
Issue 10/2014
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Abstract
Body mass index (BMI), as an approximation of general adiposity, is an established
risk factor for incidence of several adult cancer types, including colorectal cancer
(CRC). There is a common perception that these relationships extrapolate directly as
adverse prognostic factors after diagnosis, but evidence for this is lacking. The
paper from Sclesinger et al. in this issue of the journal adds a new dimension to
this debate focusing on relationships of post-diagnosis BMI (as a marker of the
steady-state weight among survivors) and survival, and provides evidence on a
decreased mortality risk among overweight (post-diagnosis BMI
25.0–29.9 kg/m2) compared with normal weight
(post-diagnosis BMI 18.5–24.9 kg/m2) CRC survivors—an
example of an ‘obesity paradox.’ The observation of the ‘obesity paradox’ is well
documented in the methodology literature, but perhaps, less familiar to the cancer
readership. Three broad classes of explanation are posited: (1) the associations are
true and plausible; (2) the associations are false and reflect methodological
issues; or (3) the observations represent a specific form of selection bias, known
as collider bias. The present author argues that the obesity paradox reflects the
latter—a product of a statistical bias—and emphasizes that, while these findings are
hypothesis generating, they will not alter clinical practice or recommendations.