More than 1.6 million new cases of cancer are estimated in the United States in 2016, with almost 600,000 individuals dying from the disease. Prostate cancer alone is responsible for 180,000 new diagnoses per year and remains the most common new cancer diagnosis for men.

Current treatment options for prostate cancer include surgery, radiation, high-intensity focused ultrasound, and cryotherapy. Although typically successful, these strategies carry significant risks for incontinence, erectile dysfunction, and local tissue injury. As a result, for a select subgroup of men with more indolent forms of prostate cancer, active surveillance has become the preferred management strategy. This approach entails periodic laboratory testing, with prostate-specific antigen (PSA) checks at intervals of 3-6 months, and repeat prostate biopsies every 1-2 years or earlier if indicated by PSA elevations. Treatment interventions are typically withheld unless re-biopsy results indicate progression to more aggressive disease. Prospective data comparing surgery and active surveillance have demonstrated improved quality of life outcomes with the latter approach . Not surprisingly, national registry data shows that active surveillance usage has increased from \<15% between 1990 and 2009 to \>40% between 2010 and 2013 for eligible patients . In order to ensure proper patient selection for active surveillance, MRI guided confirmation biopsies have become standard of care options. Almost one-third of patients will be found to harbor more aggressive cancer than revealed by their initial biopsy. Ideally, treatment could be delayed indefinitely for properly selected patients.

Although surveillance offers a reprieve from cancer treatment and its potential negative sequelae, this benefit appears temporary for many men. Institutional cohort data indicate that 36%-55% of men on active surveillance will require treatment for disease progression within 10 years. One notable risk factor for disease progression during surveillance is overweight and obesity. In a study of 565 prostate cancer patients on surveillance, a 50% increased risk of pathologic progression was associated with every 5 kg/m2 increase in BMI over 25. These results support additional evidence linking weight gain with an increased risk of prostate cancer recurrence after surgery. They have also prompted studies examining pre-surgical weight loss using caloric restriction to mitigate the risk associated with obesity. A low carbohydrate, ketogenic approach has been previously studied in small samples of patients with other types of cancer and also proposed for prostate cancer patients.

In brief, a ketogenic diet is a high-fat, low-carbohydrate diet that mimics the metabolic state of long-term fasting. Ketone bodies are generated mainly by ketogenesis in the mitochondrial matrix of liver cells and are subsequently exported via the blood to other organs to cover the energy demands of cells throughout the body. Ketogenic deaminated amino acids such as leucine also feed the citric acid cycle to form ketone bodies. Utilization of a ketogenic diet as an adjuvant prostate cancer therapy is particularly intriguing given recent preclinical data demonstrating that ketones function as endogenous histone deacetylase (HDAC) inhibitors. HDAC inhibitors have been shown to inhibit prostate cancer proliferation in preclinical models, and are already being studied in clinical trials. Therefore, the ketogenic diet may have a direct impact on disease progression that may extend beyond the BMI reduction achievable by caloric restriction, exercise or other weight loss strategies.