Fat in abdomen, thigh linked to higher risk of aggressive prostate cancer

“This study supports an association between body fat distribution and prostate cancer risk,” says researcher Barbra Dickerman, PhD.

Fat deposited in sites like the abdomen and the thigh are linked to an elevated risk of aggressive prostate cancer, according to a recent study.

“Previous studies of body fat and prostate cancer have focused on surrogate measures of adiposity, such as body mass index (BMI) and waist circumference,” explained Barbra Dickerman, PhD, of Harvard T.H. Chan School of Public Health in Boston.

“BMI, a measure of overall obesity, has been associated with a higher risk of advanced prostate cancer and poorer prognosis after diagnosis. Waist circumference, a measure of central adiposity, has been associated with a higher risk of advanced and high-grade prostate cancer in some, but not all, studies,” added Dr. Dickerman, working with Lorelei Ann Mucci, MPH, SCD, and colleagues.

The limitation of BMI is that it does not distinguish fat mass from lean body mass, and waist circumference does not distinguish visceral fat from subcutaneous fat, said Dr. Dickerman, noting emerging evidence points to the specific distribution of body fat as a key prognostic factor for prostate cancer outcomes.

In this particular analysis, published in Cancer (June 10, 2019 [Epub ahead of print]), a total of 1,832 Icelandic men were followed for up to 13 years. In the follow-up, 172 men developed prostate cancer, and 31 died from the disease. Amongst all men, visceral fat and thigh subcutaneous fat were linked to risk of advanced and fatal disease, respectively.

“We found that the accumulation of fat in specific areas, such as visceral fat, which is deep in the abdomen surrounding the internal organs, and thigh subcutaneous fat, which is just beneath the skin, was linked to a risk of advanced and fatal prostate cancer,” said Dr. Dickerman. “The link between visceral fat and advanced and fatal prostate cancer was stronger among men with a lower BMI. Further investigation of this phenotype is required. It’s possible that greater visceral fat may be a marker for an underlying physical activity pattern or hormonal milieu which influences both fat distribution and risk of advanced disease.”

In leaner men, fat may be preferentially deposited in the visceral depot in the presence of a particular hormonal milieu.

“If this hormonal milieu is also a risk factor for advanced prostate cancer, this may partially explain the results of our analyses stratified by BMI,” said Dr. Dickerman, adding that visceral fat is inversely associated with bioavailable testosterone and adiponectin, and more strongly associated with insulin resistance and pro-inflammatory cytokines than is subcutaneous fat.

Next:Several strong points to studyDr. Dickerman and colleagues conducted this research in the Age, Gene/Environment Susceptibility (AGES)–Reykjavik Study and noted the study has several strong points.

“A key strength of this study is the availability of CT (computed tomography) imaging, a gold-standard measure of body fat distribution, for more than 1,800 men who were free of cancer at baseline,” said Dr. Dickerman. “Some of the additional strengths include its population-based sample, long duration of follow-up, complete and reliable data on cancer outcomes obtained through registry linkage, and the availability of comprehensive data.”

Some of the limitations of the study include the fact that the number of advanced and fatal cancers was small, thus decreasing the study’s power, said Dr. Dickerman. Additionally, investigators did not assess changes in fat depots over time.

Read: Prostate cancer guideline update includes genomically informed therapies

“This study supports an association between body fat distribution and prostate cancer risk,” said Dr. Dickerman, adding the findings generate hypotheses for future research on specific interventions, such as physical activity, that may target fat loss and regional fat distribution and thus benefit clinically significant prostate cancer outcomes.

More prospective studies are required to investigate fat distribution and clinically significant prostate cancer outcomes, with attention to changes in fat stores over time, taking into account potential heterogeneity by BMI, pointed out Dr. Dickerman.

“Because the study population consisted of older, white men, the results may not be generalizable to younger, more diverse groups of men,” she said.

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