Participants who enroll in this study will undergo the platelet-rich plasma (PRP) study treatment. Participants will have a sample of blood collected and the platelets will be separated and then injected into half of the participants' scalp every 4 weeks for 12 weeks.

Inclusion Criteria:

• Women ≥ 18 years of age

• Have a clinical diagnosis of endocrine therapy induced alopecia (EIA) for breast cancer:

  • Selective estrogen receptor modulators (tamoxifen, toremifene)
  • Aromatase inhibitors (anastrozole, letrozole, exemestane)
  • Gonadotropin-releasing hormone agonist (leuprolide)

OR

• Must have a clinical diagnosis of chemotherapy induced (pCIA) alopecia with incomplete or absent regrowth of hair > 3 months after completion of chemotherapy without use of endocrine cancer-related therapy (ET) within the last 6 months
• Ludwig stage 1-3 for women
• If patient has a history of use of topical minoxidil and/or systemic spironolactone for alopecia for at least three consecutive months, then a 3 month washout is required prior to start of treatment
• Completed informed consent form

Exclusion Criteria:

• Patients who are pregnant or breastfeeding
• History of hair transplantation
• Use of any cosmetic product aimed at improving or correcting the signs of hair loss within 2weeks prior to screening. Note: patients are not permitted to use any hair loss products during the study.
• An active scalp dermatologic condition (e.g. alopecia areata, scalp psoriasis), scalp skin cancer (e.g. BCC, SCC), a pre-existing condition with sequelae on the scalp (e.g. scarring alopecia) or acute infection.
• Hereditary or acquired hematologic/coagulation disorders such as: platelet dysfunction syndrome, critical thrombocytopenia (platelet count <150,000 platelets/ul),hypofibrinogenemia, impaired coagulation, drepanocytosis (sickle cell anemia).
• Actively receiving anticoagulant medication
• Patients taking Aspirin or other NSAIDs such as Nurofen, Voltaren, Diclofenac or Naproxen, or fish-oil supplements because of its anti-platelet activity, can participate, provided medication is interrupted 7 days before beginning of the treatment.
• Planned or previous radiation therapy to the brain
• Vulnerable populations e.g. decisionally impaired (cognitive, psychiatric) or patients who, in the opinion of the investigator have a condition that precludes their ability to provide an informed consent
• Patients taking hair supplements, such as biotin or biosil, can participate, provided hair supplements are washed out 3 months prior to beginning of treatment.

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.