Randomized Phase II Trial of Letrozole With or Without Dasatinib as First and Second-line Treatment for Hormone Receptor-positive, HER2-negative Post-menopausal Breast Cancer That is Unresectable, Locally Recurrent or Metastatic

Inclusion Criteria:

- Has histologic or cytologic diagnosis of breast cancer; evidence of unresectable
locally recurrent or metastatic disease

- Has measurable or evaluable-only disease

- Is female, ≥18 yrs of age, post menopausal or surgically sterile

- HER2 negative, HR+, ER+ and/or PgR+ breast cancer

- 0-1 prior chemotherapy regimen for metastatic disease.

- Prior adjuvant or neoadjuvant chemotherapy completed at least 1 month prior

- Prior tamoxifen therapy is allowed

- No AI therapy for >1 year without recurrence

Exclusion Criteria:

- Pregnant or breast feeding

- Prior hormonal therapy for metastatic or locally recurrent disease

- >1 chemotherapy regimen for metastatic disease

- Pleural or pericardial effusion

- Serious cardiac condition