This phase II trial tests how well turkey tail mushroom (TTM) works in treating post-menopausal women with HER2-negative, estrogen receptor (ER)-positive breast cancer undergoing surgery. TTM is a common mushroom. In traditional Chinese medicine, it is used for enhancing function and removing toxins, as well as for cancer, hepatitis, and infections. There is previous evidence of significant tumor shrinkage occurring in the 2-month window between diagnosis and surgery in women who have taken TTM. Giving TTM may be effective in treating post-menopausal women with HER2-negative, ER-positive breast cancer undergoing surgery.

PRIMARY OBJECTIVE:

I. To determine changes in proliferation (Ki-67) in ER+HER2- breast cancers that receive turkey tail administration.

SECONDARY OBJECTIVES:

I. To assess associated adverse effects of coriolus versicolor extract (TTM). II. To determine if quality of life (QOL), mood and energy levels change while taking TTM.

OUTLINE:

Patients receive TTM orally (PO) twice daily (BID) starting at the time of study registration and continuing up to the day prior to standard of care (SOC) surgery (up to 20-42 days) in the absence of disease progression or unacceptable toxicity.

After completion of study treatment, patients are followed up 7-30 days after last dose.

Inclusion Criteria:

• Women ≥ 18 years of age

• Histological confirmation of ER+, HER2- breast cancer, newly diagnosed and tissue available for central confirmation of Ki-67 measurement. Subjects are eligible if they have a Ki-67 of ≥10%. Ki-67 will be repeated for patients who have had this done externally.

• Scheduled for definitive breast surgery

• Detectable disease as defined by mammography, breast ultrasound of greater than 5mm in size.

  • NOTE: Tumor lesions in a previously irradiated area are not considered measurable disease; Disease that is measurable by physical examination only is not eligible

• Post menopausal as defined by:

  • Self-reported last menstrual period greater than 12 months, or
  • Bilateral oophorectomy, or
  • Follicle stimulating hormone (FSH) >20 mIU/mL, and estradiol level ≤ 20 pg/mL

• Not taking aromatase inhibitor or a selective estrogen receptor modifier

• Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0, 1 or 2 obtained ≤ 90 days prior to registration

• Platelet count ≥ 100,000/mm^3 (obtained ≤ 90 days prior to registration)

• Absolute neutrophil count (ANC) ≥ 1,000/mm^3 (obtained ≤ 90 days prior to registration)

• Hemoglobin ≥ 11 g/dL (obtained ≤ 90 days prior to registration)

• Serum transaminase [alanine aminotransferase (ALT) or aspartate aminotransferase (AST)] ≤ 1.2 x upper limit of normal (ULN) (obtained ≤ 90 days prior to registration)

• Alkaline phosphatase ≤ 1.2 x ULN (obtained ≤ 90 days prior to registration)

• Serum creatinine ≤ 1.2 x ULN (obtained ≤ 90 days prior to registration)

• Provide written informed consent

• Ability to complete the Symptom Experience Diary by themselves or with assistance

Exclusion Criteria:

• Ki-67 of <10%

• Current use of any medicinal mushrooms

• Patient with locally advanced cancer who will require neoadjuvant therapy or metastatic cancer

• Currently on systemic chemotherapy

• Concurrent endocrine therapy (selective estrogen receptor modifiers or aromatase inhibitors)

• Allergy to mushrooms

• Co-morbid systemic illnesses or other severe concurrent disease which, in the judgment of the investigator, would make the patient inappropriate for entry into this study or interfere significantly with the proper assessment of safety and toxicity of the prescribed regimens

• Immunocompromised patients

• Patients known to be HIV positive and currently receiving antiretroviral therapy.

  • NOTE: Patients known to be HIV positive, but without clinical evidence of an immunocompromised state, are eligible for this trial

• 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

• Receiving any other investigational agent which would be considered as a treatment for the primary neoplasm

• Other active malignancy 3 years prior to registration

  • EXCEPTIONS: Non-melanotic skin cancer or carcinoma-in-situ of the cervix
  • NOTE: If there is a history of prior malignancy, they must not be receiving chemotherapy treatment for their cancer