Mediterranean diet score was modestly associated with time to grade group progression.
Men on active surveillance for prostate cancer may benefit from adherence to Mediterranean diet principles, according to results of a study conducted by investigators from the University of Texas MD Anderson Cancer Center, Houston.
The research, which was presented during the 2020 European Association of Urology Virtual Congress,1 evaluated Gleason grade group progression in men with newly diagnosed localized prostate cancer enrolled in a prospective active surveillance trial. A Mediterranean diet score (MDS) was calculated for each participant who completed a baseline food frequency questionnaire, and the population was divided into tertiles based on the MDS. A higher MDS reflects greater adherence to the Mediterranean dietary pattern.
During a median follow-up of 36 months, 76 men (18.5%) progressed. Results from a Cox proportional hazards model controlling for clinical characteristics showed that the MDS was modestly associated with time to grade group progression, reported Justin Gregg, MD, assistant professor of urology at The University of Texas MD Anderson Cancer Center.
Compared with the reference group of men in the lowest MDS tertile, there was little difference in risk of progression over time for men with a middle range MDS (hazard ratio [HR] and 95% confidence interval [CI]: 1.02 [0.61-1.70]; P =0.93). Higher MDS adherence appeared to be associated with lower risk of grade progression (HR and 95% CI for the highest vs lowest tertile: 0.63 [0.33-1.19]; P-trend=0.06). In analyses stratifying men by clinical factors, the general trend favoring a higher MDS for reducing progression risk was maintained across various subgroups.
The investigators stated that further work is needed to identify subgroups who may benefit from diet interventions based on the Mediterranean diet.
“We are currently evaluating this further in a prospective fashion,” Gregg said.
The study in which the data were collected was started at MD Anderson Cancer Center in 2005. Although it enrolled about 1000 men, the analysis of the association of MDS and prostate cancer progression included only 410 men who had baseline dietary information from the food frequency questionnaire that provided data to determine the MDS.
The MDS, which is calculated across 9 energy-adjusted food groups, has a possible range of 0 to 9. Approximately one-third of the 410 men included in the study had an MDS score in the lowest tertile (MDS 0-3), 41.5% were in the middle tertile (MDS 4-5), and approximately 25% were in the highest tertile (MDS 6-9).
Gabriel Haas, MD, moderated the virtual session. He commented that he was surprised by study results indicating benefit of Mediterranean diet adherence in healthier patients—those who did not have diabetes or hypercholesterolemia—but not in patients who had diabetes or who were statin users.
Offering an explanation for the data, Gregg stated the need to be cautious interpreting the findings for the diabetic cohort because of its relatively small size. Nevertheless, he suggested that the findings are consistent with the idea that a Mediterranean diet can affect prostate cancer progression through lowering of systemic inflammation.
“The possibility that someone who has diabetes already has a high level of inflammation that cannot be counterbalanced by the Mediterranean diet may be a hypothesis worth looking at,” Gregg said.
Addressing the association with statin use, Gregg said, “The Mediterranean diet may have more potential impact among men who are not taking a medication that affects inflammation.”
1. Gregg JR, Zhang X, Zheng J, et al. Association of Mediterranean diet score and disease progression among localized prostate cancer patients on active surveillance. 2020 European Association of Urology Virtual Congress. July 17-26, 2020. Abstract PT157