Recent research reveals that maintaining a nutritious diet may help prevent low-risk prostate cancer from becoming more aggressive in men who are being monitored through active surveillance. This approach involves closely tracking lower-risk cancer patients instead of immediately opting for treatments that may lead to unwanted side effects or complications.
The results of this study have been published in the journal JAMA Oncology.
According to Bruce Trock, Ph.D., a professor of urology, epidemiology, and oncology at Johns Hopkins University School of Medicine and director of the Brady Urological Institute’s epidemiology division, “Many men diagnosed with low-grade prostate cancer are eager to know what they can do to decrease the likelihood of their tumors becoming more aggressive, and dietary changes are among the most frequently asked questions. These men wish to make beneficial changes to enhance their prognosis. This motivated us to collect information about their diets, lifestyles, and exposures for the past 20 years. We hope these new findings will help us create specific recommendations to reduce cancer progression risks.”
When prostate cancer is identified via biopsy, the cells are classified into grade groups based on their appearance compared to normal prostate tissue. Grades range from 1 to 5, with grade 1 signifying slow-growing cancer cells that closely resemble normal tissue and do not spread, while grade 5 represents cells that appear significantly abnormal and can grow and metastasize if untreated. These classifications indicate the biological aggression of the cancer.
During active surveillance, regular biopsies are performed to monitor any changes in the prostate cancer, which might result in a higher grade classification, known as grade reclassification. This process often leads to treatment recommendations and is commonly used by researchers to assess the efficacy of therapies and lifestyle changes.
Christian Pavlovich, M.D., a professor of urologic oncology at Johns Hopkins University School of Medicine and director of the Brady Urological Institute’s active surveillance program, states, “Although prior studies have explored the link between diet and prostate cancer, we believe ours is the first to provide statistically significant evidence showing that a healthy diet correlates with a lower risk of prostate cancer progression to a higher grade group, as indicated by fewer men on active surveillance experiencing grade reclassifications over time.”
In the new study, researchers prospectively analyzed the data of 886 men (average age at diagnosis: 66) who were diagnosed with grade group 1 prostate cancer between January 2005 and February 2017. All participants were part of the Johns Hopkins Medicine active surveillance program and completed a validated food frequency survey — the Block 1998 Food Frequency Questionnaire — detailing their typical dietary habits. Among the participants, 55 were Black (6.2%), 803 (90.6%) were white, and 28 (3.2%) identified as belonging to other races or ethnicities.
Based on the participants’ responses, a Healthy Eating Index (HEI) score was assigned to each, which ranges from 0 to 100.
Zhuo Tony Su, M.D., the lead author and a fifth-year resident at the Brady Urological Institute, explains, “The HEI is a recognized measure of overall diet quality, which gauges how closely an individual’s eating habits align with the U.S. Department of Agriculture’s Dietary Guidelines for Americans. We assessed each patient’s HEI score based on their dietary information collected upon enrollment in our active surveillance program to determine if a better diet quality was associated with a lower likelihood of grade reclassification in subsequent years.”
Su adds that the researchers also utilized an energy-adjusted HEI (E-HEI) score, considering each participant’s daily caloric intake.
The team also computed scores for each participant utilizing the Dietary Inflammatory Index (DII) and the energy-adjusted DII (E-DII).
“The DII and E-DII scores examine the inflammatory or anti-inflammatory potential of diets, indicating that higher scores may relate to diets likely to induce more inflammation, which can contribute to the development and progression of prostate cancer,” explains Su. “We investigated whether diets with higher inflammatory potential were linked to an increased risk of grade reclassification.”
During a follow-up at 6.5 years post-diagnosis, 187 men (21%) had been reclassified to grade group 2 or higher, 55 (6%) of whom experienced a significant increase to grade group 3 or more.
Trock notes that their analysis revealed a statistically significant inverse association between adherence to a high-quality diet, as indicated by high HEI and E-HEI scores, and the risk of grade reclassification while under active surveillance. In simple terms, higher HEI and E-HEI scores corresponded with a reduced likelihood of low-grade prostate cancer advancing to a more severe stage requiring curative treatment.
According to Pavlovich, for those patients adhering to a nutritious diet, each rise of 12.5 points in the HEI score was linked to an approximate 15% decrease in the risk of reclassification to grade group 2 or higher, and a 30% decrease in the risk of reclassification to grade group 3 or above.
The findings also suggest that a diet of higher quality could potentially lead to reduced inflammation, which may be one of several mechanisms for lowering risk. However, no connection was found between grade reclassification and the initial DII/E-DII scores.
Trock adds, “This absence of correlation with DII/E-DII could imply that inflammation is critical in the transition from a healthy prostate to one afflicted with cancer. Yet, in men with existing prostate cancer, the subtle biological transition from a lower to a higher grade might be influenced by different dietary-related mechanisms.”
The research team acknowledges several limitations, such as relying on self-reported dietary data, potential nonresponse bias—which occurs when the characteristics of respondents differ from those of nonrespondents affecting the research’s representativeness—and the lack of monitoring dietary changes over time. Additionally, they highlight that the predominantly white demographic of men diagnosed with grade group 1 may limit the generalization of these findings to all patients.
Pavlovich concludes, “The insights we’ve gained so far should assist in advising men who opt for active surveillance and wish to improve their dietary habits. Nevertheless, extensive studies involving more diverse populations are necessary to truly confirm the link between a nutritious diet and a lower risk of prostate cancer progression.”
In addition to Trock, Pavlovich, and Su, the research team from Johns Hopkins Medicine includes Patricia Landis and Mufaddal Mamawala, M.B.B.S., M.P.H.
Collaborators from other medical institutions include Claire de la Calle, M.D., from the University of Washington, and three researchers from the University of South Carolina: James Hebert, Sc.D., M.S.P.H.; Nitin Shivappa, Ph.D., M.B.B.S., M.P.H.; and Michael Wirth, Ph.D., M.S.P.H.
This research was funded by the Persky Family Foundation and the Patrick C. Walsh Prostate Cancer Research Fund.
Hebert discloses a vested interest in Connecting Health Innovations, a company that has licensed his invention of the Dietary Inflammatory Index from the University of South Carolina to create apps for clinical dietary counseling. Su reports receiving a Persky scholarship and an intramural grant from Johns Hopkins urology during this study. Trock has received consulting fees from Emmes and Myriad Genetics and grants from MDxHealth separate from this research.
No additional disclosures were reported by other authors.
