This is a pilot, single arm prospective trial assessing feasibility, safety and effects on patient nutritional status of a 5-day fasting-mimicking diet (FMD) in patients with different cancer types and concomitant anticancer treatment.

It is proposed to conduct a single-arm phase II clinical study of a FMD (Prolon, by L-Nutra) in 60 patients with solid or hematologic tumors who undergo treatment with chemotherapeutic regimens, hormone therapies, other molecularly targeted therapies (including kinase inhibitors), biological drugs (including trastuzumab, pertuzumab, cetuximab and bevacizumab) or inhibitors of immune checkpoints (e.g. Opdivo, Keytruda).

Prolon is a FMD lasting five days. It consist of vegetable soups, broths, bars, olives, crackers, herbal teas, supplements of vitamins and minerals. Day 1 of the FMD supplies ~4600 kJ (11% protein, 46% fat, and 43% carbohydrate), whereas days 2-to-5 provide ~3000 kJ (9% protein, 44% fat, and 47% carbohydrate) per day.

Primary endpoints of the study are the feasibility and safety of monthly cycles of the FMD in patients with solid or hematologic tumors who undergo active treatment. Feasibility is monitored through the compilation of a food diary and is defined as the strict adherence to the diet prescribed in all its days with the possibility of admitting the consumption of only 50% of the planned diet and / or a maximum consumption of 4-5 Kcal / kg body weight of food not provided in only one of the five days of each cycle. Furthermore, the dosage of IGF-1 and of urinary ketone bodies allow to identify further cases of non-adherence to the diet.

FMD-emergent side effects are monitored according to the NCI-CTCAE version 5.0.

Secondary endpoints include:

• patient nutritional status as monitored by weight, handgrip strength, bio-impedance and serum markers (ferritin, transferrin, colinesterase).
• Quality of life (QLQ-C30)
• Clinical responses measured by CT, MRI or by blood chemistry tests, dosing of tumor markers and / or molecular biology tests in the case of prostate tumors or hematologic tumors (e.g. PSA in patients affected by prostate cancer, BCR / Abl mRNA in the case of patients undergoing treatment with kinase inhibitors for CML; CM in the case of patients undergoing treatment for multiple myeloma).
• Long-term efficacy (progression-free survival, overall survival).
• Effect of FMD on HOMA index, PCR, circulating levels of IGF-1 and urinary levels of ketone bodies.
• Effect of FMD on lymphocyte subsets, NK cells and antigen-presenting cells with a role documented in antitumor immunity.

It is foreseen that 60 patients will be enrolled.

Inclusion Criteria:

• Written informed consent
• Age > 18 years
• Patients with solid or hematologic tumors undergoing active treatment, including patients who are preparing to start a new treatment with chemotherapeutic regimens, hormone therapies, other molecularly targeted therapies (including kinase inhibitors), biologics (including trastuzumab) , pertuzumab, cetuximab and bevacizumab) or inhibitors of immune checkpoints (eg Opdivo, Keytruda), ie patients in whom treatment is already underway;
• ECOG performance status 0-1
• Adequate organ function
• BMI >21 kg/m2 (with possibility to also enroll patients with 19\