Background: Recently, the ketogenic diet has been proposed as an adjunct treatment for a range of medical conditions including weight loss, diabetes, cancer, and neurodegenerative diseases. Because malignant CNS tumors are highly dependent on glucose, the use of a ketogenic diet as an adjunct therapy is currently being explored. This case series summarizes our experience implementing a ketogenic diet for patients with CNS malignancies.Methods: Patients diagnosed with CNS malignancies following a ketogenic diet were identified between 2015 and 2017. Malignancies included confirmed diagnoses of glioblastoma (GBM), astrocytoma, or oligodendroglioma. With guidance from a registered dietitian, ketone levels, glucose levels, and weight were regularly collected for several patients along with patient-reported symptoms and adverse effects. Interested patients were asked to follow a 3:1 ketogenic diet for 120 days. The ketogenic diet is a high-fat, moderate protein, and very low carbohydrate diet, where patients limited carbohydrate intake to ≤20 g per day. Brain imaging was reviewed. A series of descriptive analyses were conducted.Results: The ketogenic diet was initiated in 12 patients of which 8 patients contributed data on their blood glucose and ketone levels. The majority of patients were male (n = 10) with a median age of 45 (range 32-62). Diagnoses included GBM (n = 6), grade 2/3 astrocytomas (n = 5) and one patient with a grade 2 spinal cord astrocytoma. Ten of the 12 patients were receiving concurrent treatment; two received supportive care only. The majority of patients with evaluable data (n = 8) maintained ketone levels above 0.5 mM for the duration of 120-day period. Ketone levels generally increased from baseline while glucose levels and BMI decreased. Overall, patients reported improved symptoms over the course of the diet. Imaging also suggested improved disease control and reduction in vasogenic edema. Conclusion:Taking advantage of a tumor's metabolic inflexibility can have a positive impact on patients, particularly those with CNS malignancies. More structured and statistically planned clinical trials are needed to determine the margin of impact of a ketogenic diet.

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INTRODUCTION There is abundant interest in the potential therapeutic and supportive role of a ketogenic diet (KD) for glioblastoma patients. We conducted a single-arm phase 1 trial to assess the safety and feasibility of KD plus standard-of-care (SOC) in glioblastoma patients (NCT03451799). METHODS Adults within 3 months of diagnosis participated in a 16-week intervention of a classic 3:1 KD (grams fat : grams carbohydrate + protein) with dietitian support. Blood glucose and ketone levels were assessed twice daily (Keto-Mojo), with remote monitoring of daily weight and activity (Fitbit). The primary objective was to assess safety (weight stability, CTCAE) and feasibility (maintaining ketosis > 0.3mM for > 50% of study period). Secondary objectives included assessments of progression-free survival (PFS), overall survival (OS), health-related quality of life (HRQOL), and cognition (MoCA). RESULTS From 04/2018-02/2021, 14 patients were evaluable: female:male, 8:6, median age 55 years, KPS 80, BMI 24.5. MGMT promoter methylation: 6 present, 7 absent, 1 indeterminate. Adherence to KD was high, with all patients maintaining ketosis ( > 0.3mM) > 50% and 11 patients maintaining ketosis > 85% of study days. Adverse events (> Grade 2) potentially attributable to KD: appetite loss (Grade 2: 2); fatigue (Grade 2: 5); flu-like symptoms (Grade 2: 1); constipation (Grade 2: 5, Grade 3: 1). No patients were removed from study for safety reasons. HRQOL was stable, with improvements in role function (not statistically significant). MoCA score improved in 10/14 patients. Median PFS and OS from KD initiation were 11.7 and 29.1 months, respectively. CONCLUSION Our findings suggest that a supervised KD plus SOC is safe and feasible in glioblastoma patients. KD was well-tolerated with encouraging trends in HRQOL and cognition. PFS and OS in this small trial compare favorably to historical control. A multicenter phase 2 trial powered to assess efficacy is planned.

2076 Background: Facing limited treatment options, brain tumor patients are often highly motivated to use complementary therapies, including diet, to help themselves. There is now an abundance of preclinical evidence suggesting possible benefit with a ketogenic diet (KD) for brain tumor patients, but clinical evidence is still limited. Thus, we conducted a single-arm, phase 1 safety and feasibility trial of a KD among patients with recently diagnosed glioblastoma (GBM) during standard- of-care (SOC) treatment. Methods: Adults with GBM within 3 months of diagnosis followed a supervised 16-week diet intervention of a standard 3:1 KD (Fat(g):Carbohydrate+Protein(g)) plus SOC chemoradiation. Primary outcome was safety, evaluated by weekly assessments of weight and body mass index (BMI). Secondary outcomes included feasibility (pre-specified as > 50% of patients maintaining blood ketone levels > 0.3 mM over 50% of study days), progression-free survival (PFS), overall survival (OS), health-related quality-of-life (QOL), and cognitive function. Twice daily blood glucose and ketone levels, weight/BMI, physical activity, and sleep were assessed by remote monitoring. Results: Seventeen patients were evaluable: 53% women, median age 55, median Karnofsky Performance Status 85. All participants met the primary safety objective with no instances of excessive weight loss or related serious adverse events. Adherence to KD was high: all 17 patients maintained nutritional ketosis (≥0.3 mM/dL) >50% of study days, where 14 patients maintained nutritional ketosis >85% of study days. Median time to ketosis from diet initiation was 3 days. Diet-related AEs were mild and manageable; no patients came off study due to inability to tolerate KD. Median progression-free survival (PFS) and overall survival (OS) were 12.5 months and 28.6 months from KD initiation respectively. QOL, symptom control, and cognitive function remained stable or improved, although these did not reach statistical significance. Conclusions: This phase 1 trial demonstrates that KD is safe and feasible for GBM patients receiving SOC, may improve outcomes, and provides a foundation for future randomized trials to assess efficacy. Clinical trial information: NCT03451799 .

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