Evaluate RCN3028 in Treatment of Drug-Induced VMS in Breast Cancer

Inclusion Criteria:

* Female subjects (aged 20 years or order) with confirmed diagnosis of breast cancer who have completed chemotherapy and radiotherapy, and are on a stable dose of tamoxifen or aromatase inhibitors (AIs) for at least 8 weeks at baseline and will maintain the same treatment regimen and dose throughout the study.
* Reported 7 or more moderate to severe hot flashes per day (average) or 50 moderate to severe hot flashes per week at baseline.
* Screening laboratory values for hematopoietic, hepatic, and renal functions are within the following ranges:

  * Hematopoietic : Absolute neutrophil count ≥ 1,500/mm3、Platelet count ≥ 100,000/mm3
  * Hepatic : Glutamic Oxaloacetic Transaminase/Glutamic Pyruvic Transaminase ≤ 3 times upper limit of normal (ULN)、Bilirubin ≤ 1.5 times ULN
  * Renal : Creatinine ≤ 1.5 times ULN
* Having Eastern Collaborative Oncology Group (ECOG) Performance Status of ≤ 1.
* Ability to understand and follow the instructions of the investigator, including completion of the study procedures as described in the protocol (i.e., VMS episode event log).
* Able and willing to provide written informed consent.

Exclusion Criteria:

* Subjects are pregnant or breastfeeding.
* Female subjects who have childbearing potential, but they are not willing to use effective contraceptive methods during study period and for 1 week afterward.
* Subjects who have multiple primary cancers (except for completely resected basal cell cancer, stage I squamous cell carcinoma, carcinoma in situ, intramucosal carcinoma, or superficial bladder cancer or any other cancer from which the patient has been recurrence-free for at least 5 years).
* Subjects who have inoperable breast cancer (Stage IIIB/IIIC/IV).
* Subjects who have the following medical history: myocardial infarction, congestive heart failure, significant ischemic or valvular heart disease, clinically active interstitial lung disease.
* Subjects who have systolic blood pressure (BP) outside the range 100 to 150 mmHg, diastolic BP outside the range 60 to 90 mmHg, and/or heart rate outside the range 50 to 100 bpm at baseline.
* Subjects who had received treatment for hypotension within 30 days prior to screening visit.
* Subjects who have uncontrolled hyperglycemia, HbA1c ≥ 7% at baseline.
* Subjects who have clinical significant conditions such as acute myocardial infarction or stroke with 6 months of randomization.
* Subjects who have a history of Parkinson's disease.
* Subjects are taking risperidone in the 30 days prior to screening visit.
* Subjects who had participated in another clinical trial and received an investigational drug within 30 days prior to screening visit.
* Subjects having a known history of allergic reaction, hypersensitivity or clinically significant intolerance to ingredients of the study drug.
* Subjects with a current drug or alcohol abuse problem as judged by the investigator.
* Subjects who are considered unreliable as to medication compliance or adherence to scheduled appointments or for other reasons are felt to be inappropriate for inclusion in the study as determined by the investigators.
* Subjects who use Selective Serotonin Reuptake Inhibitors (SSRI) or Serotonin-Norepinephrine Reuptake Inhibitors (SNRI), within 4 weeks prior to screening visit.
* Subjects who use herbal or dietary supplements, including black cohosh, soy, phytoestrogens or over the counter agents known to possibly be effective for the treatment of vasomotor symptoms within 2 weeks prior to baseline.
* Subjects who have serious, unstable, or clinically significant medical or psychological conditions, which, in the opinion of the investigator(s), would compromise the subject's participation in the study.