This trial will evaluate the clinical significance of the PRO Onc assay and will assess the efficacy of HER2-targeted therapy in patients with HER2-negative breast cancer who have been identified as having HER2 overexpression/activation by the PRO Onc Assay.

This two-part trial is designed to evaluate the clinical significance of the PRO Onc assay when used in patients with metastatic HER2-negative breast cancer. The first part of this study will determine the incidence of HER overexpression/activation, as determined by the PRO Onc assay, in patients previously judged to have HER2-negative breast cancer by FISH analysis. Blood specimens will be obtained from patients with HER2-negative breast cancer; CTCs will then be isolated and tested for HER2 overexpression/activation using the PRO Onc Assay. When clinically indicated, fine needle aspiration biopsy will also be obtained and submitted for the PRO Onc Assay. If the incidence of HER2 overexpression/activation, as determined by the PRO Onc Assay, is >10%, the study will proceed to Part 2. Part 2 of this study will assess the efficacy of HER2-targeted therapy in a group of patients with HER2-negative breast cancer who are identified as having HER2 overexpression/activation by the PRO Onc Assay. Patients will be treated with either trastuzumab or pertuzumab. Patients who progress during the first 8 weeks will have HER2-targeted treatment discontinued and will be removed from study. After 8 weeks, patients who have stable disease will be allowed to add chemotherapy to HER2-targeted therapy. Patients who have an objective response to single-agent, HER2-targeted therapy after 8 weeks will continue single-agent therapy.

Inclusion Criteria:

Part I

1. Women with HER2-negative breast cancer, as defined by FISH testing. (FISH testing may have been performed on the primary tumor, or subsequently on a biopsy of a metastatic lesion.)

2. Patients should be currently receiving chemotherapy, or scheduled to start chemotherapy (second-line or subsequent), for HER2-negative metastatic breast cancer.

3. To begin protocol treatment, patients must have progressed after at least 1 previous chemotherapy regimen for metastatic breast cancer.

4. Patients who are ER/PR positive or negative are eligible. ER/PR positive patients should be refractory to hormonal therapy, or not good candidates for hormonal therapy due to clinical features.

5. ECOG performance status of 0, 1 or 2.

6. Adequate recovery from recent surgery; ≥ 1 week must have elapsed from the time of a minor surgery; ≥ 4 weeks must have elapsed from the time of a major surgery.

7. Patients must have measurable disease per RECIST criteria.

8. Laboratory values as follows: Absolute neutrophil count (ANC) ≥1500/μL Hemoglobin (Hgb) ≥10 g/dL Platelets ≥100,000/L AST or ALT and alkaline phosphatase (ALP) must be <2.5 x ULN, or <5 x ULN in patients with liver metastases. Total bilirubin <1.5 x the institutional ULN Serum creatinine <1.5 x institutional ULN or calculated creatinine clearance ≥45 mL/min

   Patients from Part 1 who have HER2 overexpression/activation identified by the PRO Onc Assay may enter the treatment portion of Part 2, if they meet all Part 2 eligibility criteria.

9. Life expectancy of ≥ 12 weeks.

10. Patient must be accessible for treatment and follow-up.

11. Patients must be able to understand the investigational nature of this study and give written informed consent prior to study entry.

Part II

1. Women with HER2-negative breast cancer, as defined by FISH testing. (FISH testing may have been performed on the primary tumor, or subsequently on a biopsy of a metastatic lesion.)

2. Patients should be currently receiving chemotherapy, or scheduled to start chemotherapy, for HER2-negative metastatic breast cancer.

3. Patients who are ER/PR positive or negative are eligible. ER/PR positive patients should be refractory to hormonal therapy, or not good candidates for hormonal therapy due to clinical features.

4. ECOG performance status of 0, 1 or 2.

5. Adequate recovery from recent surgery; ≥ 1 week must have elapsed from the time of a minor surgery; ≥ 4 weeks must have elapsed from the time of a major surgery.

6. Patients must have measurable disease per RECIST criteria.

7. Laboratory values as follows:

   • Absolute neutrophil count (ANC) ≥1500/μL
   • Hemoglobin (Hgb) ≥10 g/dL
   • Platelets ≥100,000/uL
   • AST or ALT and alkaline phosphatase (ALP) must be <2.5 x ULN, or <5 x ULN in patients with liver metastases.
   • Total bilirubin <1.5 x the institutional ULN
   • Serum creatinine <1.5 x institutional ULN or calculated creatinine clearance ≥45 mL/min

8. Life expectancy of ≥ 12 weeks.

9. Patient must be accessible for treatment and follow-up.

10. Patients must be able to understand the investigational nature of this study and give written informed consent prior to study entry.

11. Patients who are eligible for HER2-targeted treatment will begin this treatment at the first time a treatment change is necessary (i.e. at the next progression of metastatic breast cancer). This may occur immediately after PRO Onc assay results are received, or may be several months later, for patients responding well to their current chemotherapy.

12. Patients must continue to meet all inclusion and exclusion criteria for the Part 2 screening population at the time they are ready to start HER2-targeted treatment.

13. Ejection fraction ≥ 50%, as measured by echocardiogram (ECHO) or MUGA.

Exclusion Criteria:

Part I:

1. Patients currently responding to hormonal therapy.

2. Previous treatment with any HER2-targeted agent.

3. Patients with meningeal metastases.

4. Patients who are not considered likely candidates for subsequent therapy after next progression of metastatic breast cancer.

5. Women who are pregnant or lactating.

6. Patients with New York Heart Association class II or greater congestive heart failure.

7. Any of the following ≤6 months prior to starting study treatment:

   • myocardial infarction;
   • severe unstable angina;
   • ongoing cardiac dysrhythmia

8. Concurrent severe, intercurrent illness including, but not limited to, ongoing or active infection, or psychiatric illness/social situations that would limit safety and compliance with study requirements.

9. Mental condition that would prevent patient comprehension of the nature of, and risk associated with, the study.

10. Use of any non-approved or investigational agent ≤ 30 days of administration of the first dose of study drug. Patients may not receive any other investigational or anti-cancer treatments while participating in this study.

Part II

1. Patients currently responding to hormonal therapy.

2. Previous treatment with any HER2-targeted agent.

3. Patients with meningeal metastases.

4. Patients with active brain metastases. Patients who have received radiation or surgery for brain metastases are eligible if there is no evidence of central nervous system (CNS) disease progression, and at least 4 weeks have elapsed since treatment. Ideally, patients should not still require use of seizure medication or steroids.

5. Patients who are not considered likely candidates for subsequent therapy after next progression of metastatic breast cancer.

6. Women who are pregnant or lactating.

7. Patients with New York Heart Association class II or greater congestive heart failure.

8. Any of the following ≤6 months prior to starting study treatment:

   • myocardial infarction;
   • severe unstable angina;
   • ongoing cardiac dysrhythmia.

9. Concurrent severe, intercurrent illness including, but not limited to, ongoing or active infection, or psychiatric illness/social situations that would limit safety and compliance with study requirements.

10. Mental condition that would prevent patient comprehension of the nature of, and risk associated with, the study.

11. Use of any non-approved or investigational agent ≤ 30 days of administration of the first dose of study drug. Patients may not receive any other investigational or anti-cancer treatments while participating in this study.

12. Past or current history of neoplasm other than the entry diagnosis with the exception of treated non-melanoma skin cancer or carcinoma in situ of the cervix, or other cancers cured by local therapy alone and a DFS ≥5 years.

Excludes patients with no circulating tumor cells for the PRO Onc Assay

18 Months