Inclusion Criteria:

          -  Histologically confirmed solid tumor malignancy for which single agent PD-1/PDL1
             inhibition immunotherapy is recommended as standard of care therapy. Acceptable
             PD-1/PD-L1 inhibitors include:

               -  Pembrolizumab

               -  Nivolumab

               -  Cemiplimab

               -  Atezolizumab

               -  Avelumab

               -  Durvalumab

               -  Additional PD-1/PD-L1 inhibitors may be considered, with the approval of the
                  principal investigator (PI)

          -  Advanced or metastatic cutaneous tumor with measurable disease evaluable by RECIST
             criteria. Patients with other solid tumors may be eligible if they have a cutaneous
             metastasis amenable to biopsy (with approval of PI only)

          -  No more than 2 lines of prior systemic therapy (not including neoadjuvant or adjuvant
             therapy)

          -  Eastern Cooperative Oncology Group (ECOG) performance status 0-1

          -  Absolute neutrophil count >= 1,000/mcL

          -  Absolute lymphocyte count >= 500/mcL

          -  Hemoglobin >= 8.0 g/dL

          -  Platelets >= 75,000/mcl

          -  Total bilirubin =< 1.5 x institutional upper limit of normal

          -  Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase
             [SGOT])/alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase [SGPT])
             =< 3 x institutional upper limit of normal

          -  Creatinine =< 1.8 mg/dl or calculated creatinine clearance > 40 ml/min

          -  Women of child-bearing potential and men must agree to use adequate contraception
             (hormonal or barrier method of birth control; abstinence) prior to study entry, for
             the duration of study participation, and for 90 days following completion of therapy.
             Should a woman become pregnant or suspect she is pregnant while participating in this
             study, she should inform her treating physician immediately

          -  A female of child-bearing potential is any woman (regardless of sexual orientation,
             having undergone a tubal ligation, or remaining celibate by choice) who meets the
             following criteria:

               -  Has not undergone a hysterectomy or bilateral oophorectomy; or

               -  Has not been naturally postmenopausal for at least 12 consecutive months (i.e.,
                  has had menses at any time in the preceding 12 consecutive months)

          -  Body mass index (BMI) >= 18.5

          -  Ability to understand and the willingness to sign a written informed consent and
             comply with short-term fasting during study and other study-related procedures

        Exclusion Criteria:

          -  Patients with history of diabetes mellitus are not eligible for this study

               -  Note: patients with pre-diabetes or a history of diabetes which subsequently
                  resolves, who are not taking metformin or any other diabetes medications are
                  eligible

          -  Patients with recent significant or unexplained weight loss that the investigator
             feels may pose an unacceptable risk for enrollment should be excluded. (Candidates who
             are overweight and have intentionally lost weight via diet or exercise should be
             excluded, for instance)

          -  Subjects on medications that may not be safely stopped during the fasting portion of
             the study, or which may not be safely consumed without food

          -  Prior history of syncope with caloric restriction in the past or other medical
             comorbidity which would make fasting potentially dangerous

          -  Prior treatment with any agent that blocks the PD-1 or PD-L1 pathway

          -  Prior treatment with other immune modulating agents within fewer than 4 weeks, prior
             to the first dose of PD-1/PD-L1 inhibition. Examples of immune modulating agents
             include blockers of CTLA-4, 4-1BB, OX-40, therapeutic vaccines, or cytokine therapies

          -  Patients must not be receiving other concomitant biologic therapy, hormonal therapy,
             chemotherapy, other anti-cancer therapy or any other investigational agents while on
             this protocol

          -  Radiation therapy, non-cytotoxic agents or investigational agents in the 4 weeks prior
             to the first dose of PD-1/PD-L1 inhibition

          -  Immunosuppressive systemic corticosteroids equivalent to prednisone 10 mg or greater
             in the 14 days prior to the first dose of PD-1/PD-L1 inhibition

          -  Any major surgery within 14 days prior to the first dose of PD-1/PD-L1 inhibition.
             Patients must have recovered from any major complications before registration

          -  Active autoimmune disease requiring systemic treatment in the past 2 years (i.e. use
             of disease modifying agents or immunosuppressive drugs). Replacement therapy (e.g.
             thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or
             pituitary insufficiency, etc) is not considered a form of systemic treatment

          -  Patients with known brain metastases should be excluded from this clinical trial
             because of their poor prognosis and because they often develop progressive neurologic
             dysfunction that would confound the evaluation of neurologic and other adverse events

          -  History of allergic reactions attributed to compounds of similar chemical or biologic
             composition to PD-1 or PD-L1 inhibitor

          -  Uncontrolled intercurrent illness including, but not limited to, ongoing or active
             infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac
             arrhythmia, or psychiatric illness/social situations that would limit compliance with
             study requirements

          -  Positive pregnancy test, active pregnancy or nursing/breast-feeding, due to the
             potential for congenital abnormalities and the potential of this regimen to harm
             nursing infants

          -  History of solid organ or bone marrow transplantation