Overview

Activating the immune system to kill cancer cells is a promising therapeutic strategy for some patients with cancer. Unfortunately, current immune-targeting treatments do not work for patients with prostate cancer. In animal models of cancer, fasting can reprogram the body's metabolism and immune cell function to help immune cells kill cancer cells. The purpose of this study is to determine whether 7 days of water-only fasting or a very low-calorie diet is safe and feasible for patients with metastatic prostate cancer. This will help the investigators develop future studies to test whether incorporating periods of fasting or very low calorie diets into treatment plans for prostate cancer can improve outcomes from this disease.

Eligibility

Inclusion Criteria:

1. Eastern Cooperative Oncology Group (ECOG) Performance Status 0 or 1
2. Age ≥18 years
3. Diagnosis of metastatic adenocarcinoma of the prostate
4. Must have a soft tissue metastasis amenable to biopsy
5. Prostate-specific antigen (PSA) is not currently declining, as determined by most recent 2 measurements taken at least 1 week apart in previous 2 months.
6. BMI between 20 and 35 kg/m2
7. Prior treatment with any prostate cancer therapy is permitted if >2 weeks from last dose. Patients are not required to have received prior treatment for prostate cancer.
8. Prior treatment with steroids is permitted if >2 weeks from last dose. Patients who cannot be weaned off steroids are not eligible.
9. Acceptable liver function:
   1. Bilirubin < 2.5 times institutional upper limit of normal (ULN)
   2. Aspartate transaminase (AST) (SGOT) and Alanine transaminase (ALT) (SGPT) < 2.5 times ULN
10. Acceptable renal function: glomerular filtration rate (GFR) of 50 mL/min/1.73 m2 or

    higher. GFR will be estimated by the 2021 chronic kidney disease epidemiology (CKD-EPI) creatinine equation1 using the online calculator found on UpToDate.com

11. Acceptable hematologic status:
    1. Absolute neutrophil count (ANC) ≥ 1500 cells/mm3 (1.5 ×109/L)
    2. Platelet count ≥ 100,000 platelet/mm3 (100 ×109/L)
    3. Hemoglobin ≥ 8 g/dL.
12. Acceptable electrolyte and acid/base status:
    1. Sodium 135-148 millimoles (mM) per litre
    2. Potassium 3.5-5.1mM
    3. Carbon Dioxide 21-31mM
    4. Phosphorus 2.7-4.5mM
    5. Magnesium ≥1.6mM
    6. Lactate ≤2mM
13. Ability to understand and willingness to sign a written informed consent document

Exclusion Criteria:

1. ECOG Performance status ≥2
2. Unintentional weight loss greater than or equal to 5% in previous 3 months
3. Diabetes mellitus, defined as HbA1c ≥6.5% or use of medications for diabetes
4. Active uncontrolled infection. Patients with a history of HIV/AIDS may be eligible if cluster of differentiation 4 (CD4)+ T cell counts are ≥ 350 cell/ul, the patient have had no opportunistic infection within the past 12 months, the patient have been on established antiretroviral therapy (ART) for at least four weeks, and the HIV viral load is less than 400 copies/ml prior to enrollment. Patients with a history of hepatitis C virus (HCV) infection are eligible if the patient have completed curative antiviral treatment and the HCV viral load is below the limit of quantification.
5. Use of immunosuppressive medications including steroids
6. Use of diuretics or beta blockers
7. History of cardiac arrythmia, myocardial infarction, valvular heart disease, or pulmonary hypertension
8. Abnormal screening EKG
9. Daily alcohol consumption
10. Any condition or mental impairment that may compromise the ability to give informed consent, patient's safety or compliance with study requirements as determined by the investigator