Obese men who undergo surgery for prostate cancer are more likely than their non-obese peers to experience a rise in prostate-specific antigen (PSA) levels, a sign that their disease is returning, new research suggests. Moreover, this seems to be true even in cases in which all of the cancer was apparently removed at surgery.

“This finding suggests that obesity may be associated with a biologically more aggressive form of prostate cancer,” the researchers state in the Journal of Urology.

In a previous study, Dr. Stephen J. Freedland, from the Johns Hopkins School of Medicine in Baltimore, and colleagues, linked obesity with an increased likelihood that not all cancer will be removed by surgery and with a rise in PSA levels.

However, it was unclear if obesity, in and of itself, was actually tied to the increase in PSA. For example, an obese body shape can make it technically difficult for the surgeon to remove all of the cancer. If some cancer is left behind then this might be responsible for the rise in PSA, not the obesity per se.

To solve this puzzle, the researchers only studied men who apparently had all of their cancer removed during surgery. A total of 731 men were included in the study.

Compared with normal weight men, obese men were four times more likely to experience an increase in PSA levels after surgery.

Further studies are needed to better understand how obesity may produce this effect on prostate cancer, Freedland’s group notes.

SOURCE: Journal of Urology, August 2004.