In this study, Fang et al explored the relationship between melanoma outcomes, obesity, and chronic inflammation. Obesity has been associated with development of cancers including melanoma. Adipose tissue produces signaling molecules, such as leptin, which are thought to play a role in cancer progression. Signaling from fat tissue may result in chronic inflammation, as happens in patients with psoriasis, a disease with a well-described relationship to obesity. The authors of this study use C-reactive protein (CRP) as a marker to measure chronic inflammation in patients with melanoma to test whether higher amounts of inflammation result in worse outcomes.
Obese patients in this study had worse overall and melanoma-specific survival. They also had higher CRP levels, which correlated with worse melanoma-specific survival. When the authors controlled for CRP, obesity was no longer an independent risk factor for survival, implying that the reason obese patients did worse was because their adipose tissue was creating a chronic inflammatory state, not that their obesity was independently affecting their mortality.
One limitation of this study was that, although they included 1804 melanoma patients, they only had CRP levels for 725 of them, less than half. Of note, there is a study by Calle et al that examined obesity and mortality associated with many types of cancers and did not detect an increase in melanoma mortality, although that study did not break down melanomas by stage as the Fang study did.1 The relationship between the immune system and melanoma is complex, and, although this study provides correlative evidence for the link between CRP and melanoma mortality, additional studies are warranted to further explain this relationship to better guide recommendations for patients.
Calle EE, Rodriguez C, Walker-Thurmond K, Thun MJ. Overweigh, obesity, and mortality from cancer in a prospectively studied cohort of U.S. adults. N Engl J Med. 2003;348(17):1625-1638. http://www.nejm.org/doi/full/10.1056/NEJMoa021423