While several studies have reported the association of weight with prostate cancer course, until now only one American study had looked for a link between obesity and tumour volume, the researchers said in a online paper in BJU International.
The new Italian study "clearly demonstrated from a clinical point of view that obesity may play a key role in prostate cancer pathophysiology, also after accounting for all possible confounders," Dr Umberto Capitanio said.
Dr Capitanio of University Vita-Salute San Raffaele, Milan and colleagues analysed data on 1,275 men who had radical prostatectomy at their centre between 2006 and 2009.
The mean BMI was 26.3 and the mean tumour volume was 5.6 mL. But in normal weight men, the mean tumour volume was 5.0 mL. It rose to 5.8, 6.3 and 9.2 mL in overweight, obese and severely obese men, respectively.
These volumes, the researchers point out are "very similar" to those seen in the American study.
BMI was an independent predictor of tumour volume even after adjustment for age, prostate-specific antigen value, clinical stage, prostate volume, and other factors.
"Besides all available confounders, obesity might provide an intrinsic microenvironment that favours cancer growth, independent of lifestyle, dietary factors and country of origin," the researchers suggest.
Dr Capitanio added, "Our results open an intriguing dilemma – whether lifestyle, dietary and metabolic control in obese patients may also affect the risk of developing a clinically significant prostate cancer."
(Reuters Health, David Douglas, August 2011)