Prostate cancer patients whose diets contain the highest amounts of plant-based foods may have a lower risk of disease progression and recurrence. Men who ate more fruits and vegetables had a 52 percent lower risk of prostate cancer progressing and a 53 percent lower risk of recurrence compared to those who ate the lowest amounts in their diets. These findings were based on diet assessments of food consumption among those enrolled in the observational Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) study.
"While not all diets are equal in terms of modifiable risk factors for prostate cancer progression, we hope these results guide people at risk to make better, more healthful choices across their entire diet," said lead author Vivian Liu, Clinical Research Coordinator of the Osher Center for Integrative Health at University of California, San Francisco. "We've known that diets that include vegetables, fruits, legumes, and whole grains are associated with numerous health benefits, including a reduction in diabetes, cardiovascular disease, and overall mortality. We can now add benefits in reducing prostate cancer progression to that list."
Liu presented the results of the study at the 2023 ASCO Genitourinary Cancers Symposium (Abstract 392).
About the Study
Decades of observational studies have found that foods such as tomatoes appear to reduce prostate cancer incidence and mortality. However, less is known about plant-based dietary patterns and prostate cancer survivorship. CaPSURE is a large multi-site study of 15,000 men started in 1999 looking at many aspects of prostate cancer. The CaPSURE Diet and Lifestyle sub-study started in 2004 and involved 2,038 men with early- to mid-stage prostate cancer.
These men completed a diet and lifestyle questionnaire that included how much and how often they consumed approximately 140 different foods and beverages. The diet indices (an overall plant-based index and a healthful plant-based index) were scored based on a composite sum of positive or negative values assigned to plant-based or animal food groups in the diet.
The researchers adjusted for days diagnosed until the first questionnaire was given, age at diagnosis, year diagnosed, total energy intake, CaPSURE clinical site, race, walking pace, smoking status, Gleason risk score at diagnosis, prostate-specific antigen level at diagnosis, and primary treatment. The researchers also inquired about various factors that could bias the assessments, including smoking status, walking pace, history of diabetes, family history of prostate cancer, household income, education level, height, body mass index, alcohol use, multivitamin use, calcium supplement use, and selenium supplement use.
These variables did not influence the results of analyses examining plant-based diets in relation to the risk of prostate cancer progression, Liu noted. The rationale for assessing walking pace was that, in past studies in this group, walking pace had been a significant predictor for progression, along with clinical factors such as age, stage, and grade, she said.
Key Findings
The researchers observed 204 (10%) progressive events (169 due to biochemical recurrence) over a median follow-up of 7.4 years. Men who reported diets that included the highest amounts of plants had a 52 percent lower risk of progression (HR: 0.48) and a 53 percent lower risk of recurrence (HR: 0.47) compared to men who ate the lowest amounts of plants.
Among men over age 65 years, greater consumption of a healthful plant-based diet was associated with a 59 percent lower risk of prostate cancer recurrence (HR: 0.41). In addition, among those with a brisk/fast walking pace (more than 3 hours/week), men who ate the highest plant-based diet had a 56 percent (HR: 0.44) lower risk of prostate cancer progression and a 59 percent (HR: 0.41) decrease in risk of prostate cancer recurrence. Associations did not vary by the participants' age, walking pace, grade at diagnosis, or cancer stage at diagnosis.
Next Steps
The researchers plan to analyze plant-based diets in relation to prostate cancer-specific mortality. They will also examine plant-based dietary measures in relation to prostate cancer-specific quality of life at 2, 5, and 10 years from diagnosis.
"Prostate cancer survivors may be recommended diet and exercise counseling to improve clinical outcomes after prostate cancer diagnosis," Liu noted.
Bradley Alexander McGregor, MD, ASCO expert in genitourinary cancers and Director of Clinical Research in the Lank Center for Genitourinary Oncology at Dana-Farber Cancer Institute, commented: "The risk of disease progression is one of many pivotal concerns for people with prostate cancer, as well as their family, caregivers, and physicians. These findings may directly inform clinical care, such as providing diet recommendations for managing health, and potentially offer other positive health benefits for preventing numerous chronic diseases."
Mark L. Fuerst is a contributing writer.