Obesity and Other Cancers

Abstract

Purpose Evidence on overweight, obesity, and an increased risk of cancer continues to accumulate and was updated in the 2016 handbook on weight control from the International Agency for Research on Cancer (IARC). The underlying primary data, together with dose-response meta-analysis and, finally, pooled analysis of individual participant data, add insight into the relation between obesity and cancer risk and prognosis. We summarize the evidence for mortality from prostate cancer, hematologic malignancies, and kidney cancer. Methods We reviewed pooled analysis of rare end points across cohorts, regardless of primary results reported from the individual studies, further reducing risk of publication bias. Of these cancer sites, only kidney cancer was included in the IARC 2002 report, although mortality from prostate cancer and hematologic malignancies was noted in the American Cancer Society prospective cohort study in 2003. The 2016 update from the IARC added details for prostate and hematologic malignancies, classifying the evidence as sufficient to conclude that avoiding excess body fatness lowers the risk of multiple myeloma but found that the evidence for it lowering the risk of prostate cancer mortality or diffuse large B-cell lymphoma was limited. Results A higher body mass index is associated with an increased risk of advanced prostate cancer and prostate cancer mortality and is associated with worse survival in most subtypes of hematologic malignancies, in a dose-response fashion. Evidence for kidney cancer is built mostly on retrospective data, which supports an obesity paradox in patients with the clear cell variant; however, population-based cohort data indicate that a higher cohort-entry body mass index is associated with worse kidney cancer–specific survival. Conclusion Together, these data add support to the evidence for a growing cancer burden caused by adiposity in both early adult and later adult life, yet leave open the question of the means of weight management after diagnosis as a strategy to improve survival.