Prostate cancer is the most common form of cancer among Canadian men and the third leading cause of cancer death. Abdominal obesity appears to be associated with a greater risk of developing aggressive prostate cancer. This link was demonstrated in a study led by Marie-Élise Parent, MD Professor of cancer epidemiology at Institut national de la recherche scientifique (INRS), and published in the journal Cancer Causes & Control.
Obesity is associated with a range of health outcomes that are of clinical and public health significance, including cancer, and over the years, several studies have shown that obesity is a major risk factor for prostate cancer.
To further explore the link between disease incidence and body mass, the research team studied data from a survey conducted in Montréal between 2005 and 2012. Researchers observed that abdominal obesity was associated with an increased risk of aggressive cancer.
The results of the study, funded in part by the Canadian Cancer Society, the Cancer Research Society, Fonds de recherche du Québec-Santé, Ministère de l’Économie et de l’Innovation, the Canadian Institutes of Health Research, were published in Cancer Causes & Control in April 2021 
“Pinpointing the risk factors for aggressive cancer is a big step forward in health research because it’s the hardest to treat,” Parent said.
“This data creates an opportunity to work preventively, by monitoring men with this risk factor more closely,” she added.
As part of the study, the researchers investigated associations between body size trajectories and prostate cancer incidence in a population-based case-control study in Montreal, Canada. The study included prostate cancer patients (n = 1,931), aged ≤ 75 years, who were diagnosed between 2005-2009, and a control group of men (n = 1,994) selected from the electoral list.
The researchers conducted interviews to assess body mass index (BMI) and Stunkard’s silhouette at ages 20, 40, 50, 60 years and measured current waist and hip circumferences. They used a predictive model to estimated waist circumference in the past. BMI and waist circumference trajectories were determined to identify subgroups. And finally, logistic regression estimated odds ratios (OR) and 95% confidence intervals (CI) for the association between anthropometric indicators and prostate cancer,
The researchers found that study participants with a current BMI ≥ 30 kg/m2 had a lower risk of overall prostate cancer (OR 0.71, 95% CI 0.59–0.85). They also observed that associations with adult BMI followed similar trends for less and more aggressive tumors, with stronger inverse relationships in early adulthood.
In contrast, the researchers noted that current waist circumference ≥ 102 cm was associated with an elevated risk of high-grade prostate cancer (OR 1.33, 95% CI 1.03–1.71).
The researchers observed that men with increasing BMI or waist circumference adult trajectories had a lower risk of prostate cancer, especially low-grade disease than those in the normal-stable range. This was especially evident among men in the obese-increase group for BMI and waist circumference.
Abdominal and general obesity
The actual distribution of body fat appears to be a significant factor in the development of the disease: the impact on a person’s health can vary depending on whether the fat is concentrated around the abdomen or distributed throughout the body.
According to Éric Vallières, a Université de Montréal student conducting his doctoral research at INRS and the study’s main author, “Abdominal obesity causes hormonal and metabolic variations that can promote the growth of hormone-dependent cancer cells. Abdominal obesity is believed to be associated with a decrease in testosterone, as well as a state of chronic inflammation linked to the development of aggressive tumors.”
General obesity did not show the same correlation as abdominal fat. This may result from a detection bias and possible biological effects.
“In obese people, the protein used to detect prostate cancer at an early stage, prostate-specific antigen (PSA), is diluted in the blood,” Vallières said.
“This hemodilution makes cancer more difficult to detect,” he added.
The research team believes that studies on the timing of obesity exposure over a lifetime should be prioritized and that a more in-depth analysis of body fat distribution could provide greater insight into the risks of developing prostate cancer.
 Vallières E, Mésidor M, Roy-Gagnon MH, Richard H, Parent MÉ. General and abdominal obesity trajectories across adulthood, and risk of prostate cancer: results from the PROtEuS study, Montreal, Canada. Cancer Causes Control. 2021 Jun;32(6):653-665. doi: 10.1007/s10552-021-01419-z. Epub 2021 Apr 5. PMID: 33818663.
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