GOTHENBURG, Sweden — Obese men, ie those with a high body mass index (BMI) and large waist circumference, have a greater risk of both high-grade, aggressive prostate cancer and prostate-cancer death than men with normal BMI and waist circumference, new data from a large European study reveals.
The study of over 140,000 men from eight countries showed that there was a linear association between BMI and waist circumference and high-grade prostate cancer and prostate-cancer death, with the risks increasing by more than 10% with each stepwise increase in adiposity.
Another notable finding from the investigation, which was presented at the European Obesity Summit 2016, was that, paradoxically, the overall risk of prostate cancer was lower for men with a higher BMI and those with a larger waist circumference.
Lead researcher Aurora Perez-Cornago, PhD, at the Cancer Epidemiology Unit, Nuffield Department of Population Health, University of Oxford, United Kingdom, explained that, when they initially analyzed the data, they realized that there were differences in incidence by cancer grade.
She told Medscape Medical News: "That forced us to divide the study in those that have high-grade and low-grade disease, so we can't actually take into account the result for total prostate cancer."
However, she noted that the lower overall risk of prostate cancer in men with greater adiposity was driven by a substantially lower risk of low-grade disease, although it was not clear what was underlying the difference.
The team concludes in a press release: "The findings from this large prospective study show that the association between body size and prostate cancer is complex and varies by disease aggressiveness; men who have greater adiposity have an elevated risk of high-grade prostate cancer and prostate-cancer death."
They continue: "Our results are in line with health advice for other noncommunicable diseases. Men should try to maintain a healthy weight."
Commenting, Jason Halford, PhD, of the European Association for the Study of Obesity and the University of Liverpool, United Kingdom, said that this sort of study is "very, very important" because it shows that a lot of the increasing health issues in the aging population linked to cancer are "related to lifestyle factors that lead to weight gain."
He noted: "So there is a clinical imperative to manage individuals, but there's also a population-based imperative, because you've got to have both a population and an individual approach to deal with this, and these data tell me that we need to be doing a great deal more on both."
Dr Halford believes that the current findings may help to strengthen public-health messages around obesity. He told Medscape Medical News: "I think cancer has more of a valence for people than perhaps diabetes does."
He said that, while people are "not really too aware of type 2 diabetes" until they are diagnosed with it and cardiovascular events are associated with mortality, "cancer is something that frightens people a lot."
"We don't want to frighten people to tackle the obesity problem, but I think it's something that people might become more concerned about in terms of consciousness about their life and health decisions."
However, he believes this needs to be accompanied by public-health policy changes that tackle the drivers of the "obesogenic environment," noting, "We have to make those life choices easier."
"We expect people/individuals to change, but we place them within an environment that pushes against making those changes, but also, once they've made changes, it becomes very difficult for those people to sustain them."
Data from EPIC Study With 14 Years of Follow-up
To examine the association between anthropometric factors and later prostate-cancer risk, Dr Perez-Cornago and colleagues examined data on 141,896 men with a mean age of 52 years from Italy, Spain, the United Kingdom, the Netherlands, Greece, Germany, Sweden, and Denmark who were participating in the European Prospective Investigation into Cancer and Nutritionstudy.
They gathered data on height, BMI, and waist circumference and determined the risk of prostate cancer and prostate-cancer death using Cox regression analysis, stratified by recruitment center and adjusted for education level, smoking, marital status, diabetes, and physical activity.
Over a mean follow-up of 14 years, there were 7022 incident cases of prostate cancer, 740 cases of high-grade prostate cancer, and 931 prostate-cancer deaths.
The risk of all grades of prostate cancer was significantly lower among men in the highest quintile of BMI than those in the lowest, at a hazard ratio of 0.90 (P < .001), and among men with the highest vs the lowest quintile of waist circumference, at a hazard ratio of 0.92 (P = .013).
However, men in the highest quintile of BMI had a trend for an increased risk of high-grade prostate cancer vs those in the lowest quintile, at a hazard ratio of 1.30 (P = .125), and a significantly increased risk of prostate-cancer death, at a hazard ratio of 1.35 (P = .013).
The highest quintile of waist circumference was, compared with the lowest quintile, associated with a significantly increased risk of both high-grade prostate cancer, at a hazard ratio of 1.46 (P = .003), and prostate-cancer death, at a hazard ratio of 1.55 (P < .001).
The researchers found that these increases in risk translated into a 10% increased risk of high-grade prostate cancer for every 5-kg/m2 increase in BMI and a 13% increased risk for every 10-cm increase in waist circumference.
In addition, every 5-kg/m2 increase in BMI was linked to a 14% increased risk of fatal prostate cancer, while every 10-cm increase in waist circumference was associated with an 18% increased risk of prostate-cancer death.
It was also observed that the risk of high-grade prostate cancer and prostate-cancer death was significantly increased in taller men. Specifically, the highest quintile of height was associated with a significantly increased risk of both high-grade prostate cancer and prostate-cancer death, at hazard ratios of 1.65 (P = .001) and 1.42 (P = .001).
The researchers did not examine potential mechanisms to explain this increased risk associated with height; however, Dr Perez-Cornago believes it could be due to hormonal differences when the men were going through puberty.
This study was funded by Cancer Research UK. The authors have no relevant financial relationships.
European Obesity Summit 2016; June 2, 2016; Gothenburg, Sweden. Poster PO1.077.
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