Obese Men May Have Better Survival With Advanced Prostate Cancer

When men have advanced prostate cancer, obesity might offer something of a survival advantage, a preliminary study suggests.

Researchers in Italy found that among men with prostate cancer that had spread throughout the body, those who were obese were less likely to die over the next few years.

Roughly 30% were still alive after three years, versus 20% of normal-weight and overweight men, the study found.

The researchers stressed that no one is advising men to pack on pounds as a defense against prostate cancer: Obesity is associated with a higher risk of developing and dying from various chronic ills, including a number of cancers.

But over the years, some studies have found that cancer patients with a higher body mass index (BMI) tend to survive longer -- a phenomenon sometimes called the "obesity paradox."

The new findings hint that the paradox might also apply to advanced prostate cancer.

However, one expert not involved in the study urged caution in drawing conclusions.

Critically, the reasons for the study patients' obesity, or thinness, are not clear, explained Dr. Vinayak Wagaskar, a urologist at Mount Sinai's Icahn School of Medicine in New York City.

He noted that BMI was measured only after the men had developed advanced cancer that was no longer responding to hormonal therapy -- and not right after their prostate cancer diagnosis.

That's important, in part, because certain treatments for prostate cancer -- including hormonal therapy and steroid medications -- can cause weight gain.

Plus, Wagaskar said, patients' weight could have been affected by additional medical conditions they had.

He said the study brings up an "interesting concept," but he stressed the need for more research -- with men's BMI measured at the time of diagnosis.

For the study, Dr. Nicola Fossati and colleagues at San Raffaele University in Milan looked at data on almost 1,600 men who'd been involved in previous clinical trials. All patients had metastatic prostate cancer that was not responding to hormonal therapy. Metastatic means it had spread to distant sites in the body.

While early-stage prostate cancer is highly treatable, metastatic cancer is different: About 30% of men with such advanced disease survive for five years, according to the American Cancer Society.

In this study, Fossati's team found that men with a BMI of 30 or higher -- the obesity threshold -- were 29% less likely to die over three years than those with a lower BMI.

The findings were presented Sunday at the annual meeting of the European Association of Urology (EAU), being held online. Research presented at meetings is generally considered preliminary until published in a peer-reviewed journal.

In a news release from the meeting, Fossati said, "This obesity paradox has been seen in some other cancers, possibly due to the relationship between tissue fat and cancer genomes, and more research is needed in this area."

On the other hand, he said, the findings might reflect some interaction between cancer chemotherapy and other medications.

"Obese patients in this older age group tend to be taking medication for other conditions," Fossati noted, "and we do not fully understand how these medicines interconnect."

Dr. Peter Albers, chair of the EAU's Scientific Congress Office, also cautioned that the reasons behind the obesity paradox, in general, are uncertain.

"It might be that patients with higher BMI are able to tolerate the toxicity of the treatments and their side effects better," Albers said in the release. "In prostate cancer it might be due to the protective impact of hormones found in tissue fat; and it is known that healthy men with slightly higher BMI have a higher overall life expectancy compared to very slim ones."

But, he stressed, that's all conjecture.

"Further research is needed to identify the biological mechanism behind these different outcomes," Albers said. "Until that mechanism is proven, we can't recommend any change to treatment for patients with advanced prostate cancer."

In fact, Wagaskar said, some other studies have linked obesity not only to a higher risk of developing prostate cancer, but also to "worse cancer-related outcomes."

Fossati agreed that a healthy weight range should be the goal. "Obesity is a risk factor for many cancers and other diseases," he said, "and patients should always aim for a healthy BMI of 18 to 24."