Adhering to a healthy lifestyle may offset the heightened risk of lethal prostate cancer in patients with adverse genetic risk factors, according to results of a large U.S. study.
In men at the highest risk of dying from prostate cancer, having the highest healthy lifestyle scores cut the risk of fatal disease in half, said study author Anna Plym, PhD, of Brigham and Women’s Hospital and Harvard School of Public Health, both in Boston. She presented these findings at the American Association for Cancer Research Annual Meeting 2021: Week 1 (Abstract 822).
Plym noted that about 58% of the variability in prostate cancer risk is accounted for by genetic factors, with common single-nucleotide polymorphisms (SNPs) accounting for a substantial proportion of prostate cancer susceptibility.
A recent study showed that a polygenic risk score (PRS) derived by combining information from 269 SNPs was “highly predictive” of prostate cancer, Plym said. There was a 10-fold gradient in disease risk between the lowest and highest genetic risk deciles, and the pattern was consistent across ethnic groups.
In addition, Plym noted, previous studies have suggested that a healthy lifestyle reduces lethal prostate cancer risk.
What has remained unclear is whether the risk for both developing prostate cancer and experiencing progression to lethal disease can be offset by adherence to a healthy lifestyle.
To investigate, Plym and colleagues used the 269-SNP PRS to quantify the genetic risk of prostate cancer in 10,443 men enrolled in the Health Professionals Follow-up Study. The men were divided into quartiles according to genetic risk.
The investigators also classified the men using a validated lifestyle score. For this score, one point was given for each of the following: not currently smoking or having quit 10 or more years ago, body mass index under 30 kg/m2, high vigorous physical activity, high intake of tomatoes and fatty fish, and low intake of processed meat. Patients with 1-2 points were considered the least healthy, those with 3 points were moderately healthy, and those with 4-6 points were the most healthy.
The outcomes assessed were overall prostate cancer and lethal prostate cancer (i.e., metastatic disease or prostate cancer–specific death).
No Overall Benefit of Healthy Lifestyle
At a median follow-up of 18 years, 2,111 cases of prostate cancer were observed. And at a median follow-up of 22 years, 238 lethal prostate cancer events occurred.
Men in the highest genetic risk quartile were five times more likely to develop prostate cancer (hazard ratio, 5.39; 95% confidence interval, 4.59-6.34) and three times more likely to develop lethal prostate cancer (HR, 3.43; 95% CI, 2.29-5.14), when compared with men in the lowest genetic risk quartile.
Adherence to a healthy lifestyle did not decrease the risk of prostate cancer overall (HR, 1.01; 95% CI, 0.84-1.22), nor did it affect men in the lower genetic risk quartiles.
However, healthy lifestyle did appear to affect men in the highest genetic risk quartile. Men with the highest healthy lifestyle scores had roughly half the risk of lethal prostate cancer, compared to men with the lowest lifestyle scores (3% vs. 6%).
A Counterbalance to Genetic Risk
Plym observed that the rate of lethal disease in men with the best lifestyle scores matched the rate for the study population as a whole (3%), suggesting that healthy lifestyle may counterbalance high genetic risk.
She added that previous research has confirmed physical activity as a protective factor, but more study is needed to shed light on the relative benefit of the healthy lifestyle components.
In addition, further research is necessary to explain why the benefit was limited to lethal prostate cancer risk in men with the highest genetic risk.
Plym speculated that the genetic variants contributing to a high PRS may also be the variants that have the strongest interaction with lifestyle factors. For men with a genetic predisposition to prostate cancer, she added, these findings underscore the potential value of surveillance.
“Our findings add to current evidence suggesting that men with a high genetic risk may benefit from a targeted prostate cancer screening program, aiming at detecting a potentially lethal prostate cancer while it is still curable,” she said.
Charles Swanton, MBPhD, of the Francis Crick Institute and UCL Cancer Institute in London, raised the possibility that competing risk issues could be at play.
If a healthy lifestyle leads to longer life, he asked, does that make it more likely that patients will live long enough to die from their prostate cancer because they are not dying from cardiovascular disease, complications of diabetes, etc.? In that case, is the healthy lifestyle really affecting prostate cancer at all?
Plym responded that, among those in the highest genetic risk group with an unhealthy lifestyle, the increased risk for prostate cancer exceeded the risk for other illnesses.
This study was funded by the DiNovi Family Foundation, the National Cancer Institute, the William Casey Foundation, the Swedish Society for Medical Research, and the Prostate Cancer Foundation. Plym declared no conflicts of interest. Swanton disclosed relationships with numerous companies, including Pfizer, Novartis, and GlaxoSmithKline.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.