Reishi Mushroom Extract for Fatigue And/or Arthralgias/myalgias in Patients with Breast Cancer on Aromatase Inhibitors

Inclusion Criteria:

• Age ≥ 18 years

• History of breast cancer, estrogen receptor positive (ER+), Her 2 positive ornegative

• Fatigue ≥ 4/10

• Currently post-menopausal (as defined by National Comprehensive Cancer Network (version 4.2024), taking any aromatase inhibitor in the curative setting andplanning to be on such for at least 8 weeks after registration. (Patients onconcurrent ovarian suppression [such as with leuprolide acetate, goserelin] areallowed) ; CDK 4/6 inhibitors abemaciclib, ribociclib ARE allowed

• Prior treatment: last chemotherapy ≥ 90 days prior to randomization (if treated withchemotherapy)

• On a stable dose of pain medications if pain medications are being regularly used. (i.e., no change in dosage in the past 30 days)

• If on supplements, must be on stable dose with no plan to change; not on or planningany acupuncture or other specific supportive modalities for fatigue or AIarthralgias

• Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0, 1 or 2

• White blood cell count (WBC) ≥ 3,000/mm^3 (obtained ≤ 30 days prior torandomization)

• Hemoglobin ≥ 10 g/dL (obtained ≤ 30 days prior to randomization)

• Platelet count ≥ 100,000/mm^3 (obtained ≤ 30 days prior to randomization)

• Total bilirubin ≤ 1.5 x upper limit of normal (ULN) (obtained ≤ 30 days prior torandomization)

• Alanine aminotransferase (ALT) or aspartate transaminase (AST) ≤ 1.2 x ULN (obtained ≤ 30 days prior to randomization)

• Prothrombin time (PT)/activated partial thromboplastin time (aPTT) ≤ 1.5 x ULN (obtained ≤ 30 days prior to randomization)

• Negative pregnancy test done ≤ 7 days prior to registration, for persons onconcurrent ovarian suppression only

• Provide informed consent

• Ability to complete questionnaires

• Willing to return to enrolling institution during the active monitoring phase of thestudy

Exclusion Criteria:

• Other known uncontrolled medical conditions causing fatigue such as untreatedthyroid disease, depression, fibromyalgia, chronic fatigue syndrome, infection,autoimmune disease, or active/untreated hepatitis

• Allergy to mushrooms

• On anticoagulation medication or aspirin or having a known bleeding disorder

• On any specific medication for fatigue (e.g., methylphenidate)

• Metastatic cancer diagnosis (history of nodal metastases is allowed)

• Chronic steroid use, unless on physiologic replacement doses

• Current use of any medical mushrooms

• On medications for diabetes

• History of symptomatic hypotension

• Taking CYP3A4, CYP2D6 sensitive substrates which can be located at the followinglink:

https://www.fda.gov/drugs/drug-interactions-labeling/healthcare-professionals-fdas-exampl es-drugs-interact-cyp-enzymes-and-transporter-systems

• Drugs which exhibit either >20% inhibition or >20% induction of CYP2E1 in vivo, suchas: Acetaminophen, Dapsone, Enflurane, Halothane, Isoflurane, & Theophylline

• Taking olaparib

• Any of the following because this study involves an agent that has unknowngenotoxic, mutagenic and teratogenic effects:

• Pregnant persons

• Nursing persons

• Persons on concurrent ovarian suppression who are unwilling to employ adequatecontraception (e.g., hormonal methods, barrier methods, intrauterine device,abstinence)