Safety, Feasibility and Metabolic Effects of the Fasting Mimicking Diet (FMD) in Cancer Patients

Tumor and normal cells display differential sensitivity to nutrient and growth factor deprivation. Due to high proliferation rates, most tumor cells depend on continuous energy and metabolic replenishment to renew and duplicate their intracellular components, such as lipid membranes, organelles, DNA and proteins; moreover, as a consequence of constitutive activation of oncogenic pathways, they are unable to halt their proliferation during starvation. This exposes them to acute energetic and anabolic crisis when nutrients (e.g. glucose, amino acids) and growth factors (e.g. insulin) in the extracellular environment are scarce. Starvation-induced toxicity is even higher when tumor cells are exposed to cytotoxic compounds, such as DNA damaging agents. Indeed, repair mechanisms that are essential to survive damage induced by cytotoxic chemotherapy require energy (in the form of ATP units) and metabolic precursors (e.g., nucleotides) that are potentially reduced at the tumor site during nutrient deprivation.

Conversely, cells of healthy tissues are more capable of adapting their proliferation and metabolism to the metabolic contexture. In conditions of nutrient and growth factor deprivation, most normal cells enter a quiescent proliferative status, thus reducing energy- and metabolite-requiring processes, such as DNA, lipid and protein synthesis; they also activate catabolic processes, such as autophagy, which provide the minimal amount of metabolites to survive starvation. Proliferative quiescence not only prevents the occurrence of damage to intracellular structures and orgenelles, but also favors their repair by sparing energy units and essential metabolites.

This differential response to starvation by cancer and normal cells could be potentially exploited to selectively target in vivo human cancers, while sparing healthy tissues. Cyclic fasting or a plant-based, calorie-restricted, low-carbohydrate low-protein diet known as fasting mimicking diet (FMD), are two approaches that have emerged in recent years to selectively target the metabolic vulnerabilities of malignant cells. Indeed, they are capable of inducing meaningful modifications in systemic metabolism, such as reduction of blood glucose insulin and insulin-like growth factor (IGF-1) in both mice and healthy volunteers.

Studies performed in preclinical models of several cancers have demonstrated that cyclic fasting/FMD produce synergistic anticancer effects when combined with cytotoxic chemotherapy, while protecting normal tissues and stimulating antitumor immunity. So far, only a few studies have tested the effects of fasting/FMD in healthy volunteers or cancer patients.

In healthy volunteers, three consecutive cycles of FMD have been shown to be safe and associated with meaningful changes in risk factors for chronic diseases. In cancer patients, a few small studies have demonstrated that short-term fasting (1-3 consecutive days every 3-4 weeks) is feasible and safe in combination with standard chemotherapy, including platinum-based chemotherapy. However, the effects of the FMD in cancer patients have not been investigated so far.

This study,aims to test the safety, feasibility and metabolic effects of the fasting-mimicking diet (FMD) in patients with different malignant neoplasms.

Patients highly motivated to follow the FMD in combination with their standard treatments, will be considered for enrollment in this study. All enrolled patients will be prescribed the same 5-day FMD regimen, which consists of a calorie-restricted (about 600 Kcal on day 1, 300 Kcal/day on days 2 to 5), low-carbohydrate, low-protein diet, which will be repeated every 21-28 days. A maximum of 8 consecutive FMD cycles will be prescribed. During each of the 5 days on FMD, patients will have at least one daily contact (by email or phone) with the study staff to communicate body weight, blood pressure, health conditions, adverse events and the amount of food and beverages introduced (also reported in daily food diaries). In the interval between consecutive FMD cycles, patients will not be prescribed any maintenance diet, but will receive generic dietary recommendations based on World Cancer Research Fund (WCRF 2007) or the American Cancer Society (ACS 2012) recommendations for cancer prevention and cancer survivors.

Patients with any malignancy, except for small cell neuroendocrine tumors, and any disease stage are potentially eligible for this study. Patients with a body mass index (BMI) < 20 kg/m2, as well as patients who lost more than 5% of their basal weight in the last 3 months, will be excluded from the study. Patients with severe comorbidities, or diabetes mellitus requiring pharmacologic therapies, will be also excluded. The FMD will be permanently discontinued in the case of FMD-related grade 4 adverse events (AEs) or serious adverse events (SAEs), or in the case that patient BMI goes below 20 kg/m2 during the FMD and is not restored between two consecutive FMD cycles.

Patients enrolled in this study will receive standard-of-care treatment for their tumor, including chemotherapy, radiotherapy, molecular target therapy, immunotherapy or best supportive care. Both patients with metastatic disease and patients undergoing adjuvant therapy after curative surgery will be candidate to enter this protocol.

The primary endpoint of the study is safety of the FMD in combination with standard antitumor treatments. Safety will be assessed by reporting and grading FMD-related AEs according to NCI Common Terminology Criteria for Adverse Events (CTCAEs) v 4.03. SAEs will be also reported.

FMD feasibility, FMD-induced metabolic effects, weight changes, and modifications of other blood and biochemical parameters will be secondary endpoints.

Feasibility will be assessed by evaluating the patient ability to comply with the prescribed dietary scheme. To do so, all patients will fill a daily food diary during each of the 5 days on FMD. At the end of the study, diaries will be analyzed. Based on the presence of major and minor deviations from the prescribed dietary scheme, patients will be defined as "compliant" or "not compliant".

FMD-induced metabolic effects will be quantified by measuring blood and urine metabolites and growth factors before the initiation and at completion of each FMD cycle (i.e. before resuming the normal diet). Absolute and relative metabolite and growth factor modifications will be reported. Standard metabolites (e.g. blood glucose, triglycerides, total and HDL cholesterol, urine ketone bodies) will be measured. In selected patients, plasma and whole blood fatty acids and some amino acids will be measured too.

The effect of the FMD on patient weight will be assessed by measuring absolute and relative weight changes during each FMD cycle and along with subsequent cycles.

Changes occurring in other blood parameters, including blood cell counts, aspartate and alanine transaminases, blood urea nitrogen, creatinine and uric acid, C reactive protein, total proteins and albumin, will be also measured before and at the end of each FMD cycle.

Finally, diet-induced changes in peripheral blood fatty acid and phospholipid profiles, as well as of immune cell populations, will be assessed in selected patients as exploratory analyses.