This is a single-arm prospective pilot study assessing the metabolic and immunologic effects of a modified fasting regimen in cancer patients with different cancer types and concomitant anticancer treatment.

A single-arm phase II clinical trial of a short-term modified fasting regimen (STMF) is proposed to be conducted in 100 patients with solid tumors who are candidates to receive active medical or radiotherapy treatment (or with medical treatment or radiotherapy already ongoing). Cancer treatment can be adjuvant or palliative. Patients with haematological tumors are also included. Enrolment is also foreseen for patients with haematological tumors who are not undergoing active treatment yet, but are followed with a watchful waiting approach (e.g. patients with low-risk B-CLL or low-risk follicular lymphoma). Finally, enrolment is also open to patients with relapsing forms of non-melanoma skin cancers (e.g. basalioma, epithelioma).

The primary endpoint of the study is to evaluate the effects of a STMF on the circulating levels of factors with pro- or anti-oncogenic activity (including insulin, IGF1, IGFBP1, IGFBP3 , leptin, adiponectin, IL-6, TNF-alpha, IL1beta), as well as the effect of STMF cycles on leukocyte subpopulations with a role in the control of tumor growth, such as regulatory T cells, the "myeloid-derived suppressor cells" (MDSC) as well as NK cells, and on stem cell pools (e.g. hematopoietic stem cells, endothelial stem cells, mesenchymal stem cells).

The STMF regimen that is applied is a 5-day low-calorie and low-protein diet. Patients undergo a medical exam/history collection and a nutritional assessment (body weight, handgrip strenght and bioimpedance measurement) at baseline and then at the visits that precede every cycle of STMF (i.e. once every three weeks or monthly, depending on the therapeutic regimen the patient is undergoing, and in any case no more frequently than once every three weeks - eg when combined with q21 chemotherapy regimens). Adverse events are recorded at each visit in accordance with NCI-CTCAE version 5.0. P

Inclusion Criteria:

• Written informed consent
• Age > 18 years
• Patients with solid or hematologic tumors undergoing active treatment (including chemotherapy regimens, hormone therapies, other molecularly targeted therapies - including kinase inhibitors, biologicals or inhibitors of immune checkpoints; patients in whom treatment is already ongoing are also eligible; patients with haematological malignancies who are managed by watchful waiting (e.g. low-risk B-CLL or follicular lymphoma) as well as patients with relapsing forms of non-melanoma skin cancer (basal or squamous cell carcinoma) are also eligible.
• ECOG performance status 0-1
• Adequate organ function
• BMI >21 kg/m2 (with possibility to also enroll patients with 18.5<BMI<21 based on the judgement of the treating physician)
• Low nutritional risk according to nutritional risk screening (NRS)

Exclusion Criteria:

• Age> 65 years [with the possibility to enroll from 65 to 75 years old patients if considered safe by the examining doctor
• Diabetes mellitus;
• BMI <18.5 kg/m2;
• Bio-impedance phase angle <5.0°;
• Medium/high nutritional risk according to NRS;
• Any metabolic disorder capable of affecting gluconeogenesis or the ability to adapt to periods of fasting;
• Ongoing treatment with other experimental therapies.](streamdown:incomplete-link)