Standardized Extract of Cultured Lentinula Edodes Mycelia (AHCC®) in Ovarian Cancer Patients on Adjuvant Chemotherapy

Inclusion Criteria: 1. Histologically or cytologically confirmed epithelial ovarian, fallopian tube or peritoneal carcinoma * High-grade or low-grade serous, mucinous, endometrioid, clear cell, mixed or other histologies allowed 2. Clinical stage I-IV at diagnosis 3. Treatment decision to include standard-of-care adjuvant chemotherapy after primary or interval debulking surgery, or initial staging surgery. Chemotherapy should include a platinum and a taxane doublet. * Neoadjuvant chemotherapy is allowed (no washout period will be required) * Any combination of platinum and taxane doublet is allowed (i.e., carboplatin, cisplatin, paclitaxel, or docetaxel) * Different schedules of platinum and taxane doublet are allowed (i.e., every 21 days, dose-dense or weekly) * Bevacizumab is allowed 4. Age greater than or equal to 18 years of age 5. English or Spanish-speaking individuals 6. Eastern Cooperative Oncology Group (ECOG) performance status less than or equal to 2 (Karnofsky greater than or equal to 60%) 7. Organ and bone marrow function defined by: * Leukocytes greater than or equal to 2,500/µL * Absolute neutrophil count greater than or equal to 1,000/µL * Platelets greater than or equal to 75,000/µL * Hemoglobin greater than or equal to 8 g/dL * Total bilirubin less than or equal to 1.5 × institutional upper limit of normal (ULN) (however, patients with known Gilbert disease who have serum bilirubin level less than or equal to 3 x ULN may be enrolled) * Aspartate aminotransferase (AST)/ alanine transaminase (ALT) less than or equal to 3 × ULN (AST and/or ALT less than or equal to 5 x ULN for patients with liver involvement) * Alkaline phosphatase less than or equal to 2.5 × ULN (less than or equal to 5 x ULN for patients with documented liver involvement or bone metastases) * Creatinine clearance or glomerular filtration rate (GFR) greater than or equal to 30 mL/min by Cockcroft-Gault or 30 mL/min/1.73m2 8. Individuals of child-bearing potential must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) for the duration of study participation (including dosing interruptions) and for at least 5 months (150 days) after the last dose of study agent or the duration specified in the United Surgical Partners International (USPI) for any of the agents used in the adjuvant standard-of-care regimen, whichever is longest. Patients must agree to refrain from egg donation during this timeframe. 9. Ability to understand and the willingness to sign a written informed consent document 10. Patients with known human immunodeficiency virus (HIV) are allowed in the study, but HIV-positive patients must have: * A stable regimen of highly active anti-retroviral therapy (HAART) * No requirement for concurrent antibiotics or antifungal agents for the prevention of opportunistic infections * A cluster of differentiation 4 (CD4) count above 250 cells/µL and an undetectable HIV viral load on standard polymerase chain reaction (PCR)-based tests within the last year. Exclusion Criteria: 1. History of allergic reactions to mushrooms 2. History of allergic reaction to dextrin 3. History of allergic reaction to rapeseed oil 4. History of allergic reaction to corn 5. Consumption of other supplements derived from mushrooms or basidiomycetes * Consumption of whole mushrooms through diet is acceptable * Consumption of a blend with unknown/ unclear mushrooms or basidiomycetes contents, then it is ok to include participant 6. Current or prior (within 3 months of enrollment) use of immunosuppressive medications (including, but not limited to, prednisone, cyclophosphamide, azathioprine, methotrexate, thalidomide, and anti-tumor necrosis factor (anti-TNF) agents). The following are exceptions to this criterion: * Intranasal, inhaled, topical or local steroid injections (e.g., intra-articular injection); steroids as premedication for hypersensitivity reactions; systemic corticosteroid at physiologic doses not to exceed 10 mg/day of prednisone or equivalent may be enrolled. * Patients who have received acute, low-dose, systemic immunosuppressant medications (e.g., a one-time dose of dexamethasone for nausea) may be enrolled. * The use of inhaled corticosteroids and mineralocorticoids (e.g., fludrocortisone) for patients with orthostatic hypotension or adrenocortical insufficiency is allowed. 7. 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 interfere with patient safety or limit compliance with study requirements. 8. Inability to swallow experimental agent or placebo 9. History of gastrectomy or other malabsorption syndromes 10. Subjects who are pregnant or breast-feeding 11. Any condition that would prohibit the understanding or rendering of informed consent 12. Any medical condition that in the opinion of the investigator would interfere with the patient's safety or compliance while on trial.