Adherence to Mediterranean Diet Beneficial in Early-Stage Prostate Cancer

The Mediterranean diet has long been known to improve and control health. The diet emphasizes eating vegetables, fruits, legumes, grains, and fish, and recommends limiting meat and dairy consumption. It also proposes applying moderation to consumption of foods containing saturated fat and beverages containing alcohol. Another hallmark of the Mediterranean diet is the recommendation to balance monounsaturated fats with saturated fats. Monounsaturated fats are derived from nuts, seeds, and olives; saturated fats are found in butter, other dairy products, and red meat.

Many large studies worldwide have demonstrated the success of the Mediterranean diet in patients with inflammatory and lipid disorders. Results in patients who follow the diet also demonstrate lower incidences of cardiovascular disease, insulin sensitivity, morbidity and mortality, and cancers. According to a team of researchers at the University of Texas MD Anderson Cancer Center, observational studies indicate that prostate cancer is less likely overall to develop in men who follow a Mediterranean diet eating pattern, and aggressive prostate cancer specifically. In addition, overall survival is improved in those patients who adopt a Mediterranean diet after a prostate cancer diagnosis.

In their report, the MD Anderson researchers wrote that a distinctive characteristic of prostate cancer is that more than 90% of cases diagnosed via biopsy are localized to the prostate. Of these, almost 50% are eligible for active surveillance (AS), an approach that utilizes active monitoring and delayed intervention. This is fortunate because the urinary and sexual sequelae of radical prostate cancer treatment can have a negative impact on quality of life. Looking for another way to limit disease progression as demonstrated by laboratory values and biopsy results, the researchers focused on the Mediterranean diet.

A multidisciplinary team of urologic surgeons, medical oncologists, and radiation oncologists evaluated the safety of the active surveillance protocol for the 560 patients with localized prostate cancer who were enrolled in the study. Each participant completed a baseline 170-item food frequency questionnaire (FFQ) and underwent confirmatory biopsy at enrollment; clinical examination was performed and serum prostate-specific antigen (PSA) and testosterone levels were measured every 6 months. Biopsies were repeated every 1 to 2 years; if a biopsy was negative, it was not repeated the following year.

If a positive biopsy led to a disease reclassification, the team offered the patient the option of active treatment. Disease reclassification was defined as an increase in tumor volume or Gleason grade group (GG). Patients could remain on the AS protocol provided their treating physician approved of their doing so.

After excluding patients with extreme total energy intake, 410 patients (median age 64.4 years [standard deviation, 8.5]) were included in the Mediterranean diet score analysis, which measured intake of 7 food groups and 2 macronutrients. Food groups were vegetables, fruits, legumes, whole grains, meat, fish, dairy products, alcohol intake, and monounsaturated-to-saturated fatty acids intake ratio. Moderate alcohol consumption was defined as up to 13 drinks per week.

GG progression was the primary outcome of interest, defined as any increase in disease after the confirmatory biopsy. The researchers followed all patients until one of the following occurred: the patient demonstrated grade progression, needed treatment, was lost to follow-up, elected to be removed from the study, or died or until they reached the study censor date of December 31, 2016.

The researchers found that baseline adherence to the Mediterranean diet seemed to be linked to a lower risk of GG progression in patients with localized prostate cancer who were managed on an active surveillance protocol. This result is consistent with other health findings associated with plant-based, low-fat dietary patterns, and apparently confirms that an overall healthful eating pattern is important to affect cancer-related outcomes in men with localized and low-risk prostate cancer.

Could this effect be due to statin use? The researchers examined this possibility and found that greater adherence to the Mediterranean diet lowered the risk of GG progression regardless of statin use.

Although these results are encouraging, this study was limited by its size and length of follow-up. Furthermore, the study participants were mostly men with low-risk disease, which limits how well the study specifics apply to a broader population of men with prostate cancer.

The researchers demonstrated that adhering to the basic principles of the Mediterranean diet may lower the risk of GG progression among men with localized prostate cancer who are managed with active surveillance because of its anti-inflammatory, antilipidemic, and chemopreventive properties. However, they call for larger studies to verify patient- and cancer-specific factors.

Disclosure: One author declared affiliations with or received funds from the pharmaceutical industry. Please refer to the original article for a full list of disclosures.

Reference

Gregg JR, Zhang X, Chapin BF, et al. Adherence to the Mediterranean diet and grade group progression in localized prostate cancer: an active surveillance cohort. Cancer. Published online January 7, 2021. doi:10.1002/cncr.33182