When the International Agency for Research on Cancer reviewed evidence on obesity and cancer in 2002 they concluded that only breast, colon, endometrial, esophagus, and kidney cancers were caused by obesity (International Agency for Research on Cancer 2002). Other cancers had only probable evidence for an association. Since 2002 numerous additional reports have been added from studies of obesity and hematologic malignancies supporting a direct relation between obesity and these cancers. For example, Renehan combined data form prospective studies and showed that risk of myeloma increased significantly with increasing body mass index, a measure of adiposity (Renehan, Tyson et al. 2008). Overweight and obese adults are at increased risk of myeloma.
Now a new report adds to this evidence (see report). A meta-analysis of 4 case-control studies plus 11 cohort studies confirms that high BMI increases risk of myeloma (Lichtman 2010). The likely mechanism for this causal relation is that obesity and the greater fat mass has physiologic effects on insulin pathways, inflammatory pathways, estrogens, and tumor necrosis factor-alpha (Bray 2004). In particular, for myeloma evidence relates to pathways through inflammation – IL-6 – and increased risk of disease (Cozen, Gebregziabher et al. 2006). Further understanding of this pathway may offer insights for prevention of this malignancy, which currently has relatively poor survival (US data suggest only 50% of patients survive 4 years after diagnosis).
The obesity epidemic continues to unfold and the health consequences become clearer. Obesity causes more caner than previous estimates suggested. Unfortunately all these cancers caused by obesity add to the burden on society.
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