Inclusion Criteria:

1. Histological confirmation of ER negative breast carcinoma, stage I, II, or III

2. Completed all adjuvant therapy including (if indicated) endocrine, trastuzumab,
radiation therapy

3. At least 18 years of age.

4. Provided written informed consent.

5. Adequate bone marrow function: Hemoglobin >/= 9 gm/dL. • Absolute granulocyte count
>/= 1,500/mm^3 (1.5 x 10^9/L). • Platelets >/= 75,000/mm^3 (100 x 10^9/L).

6. Normal mammogram of unaffected breast within 12 months prior to study entry.

7. Female: A female is eligible to enter and participate in the study if she is of: a.
Non-childbearing potential (i.e., women with functioning ovaries who have a current
documented tubal ligation or hysterectomy, or women who are post-menopausal); or b.
Childbearing potential (i.e., women with functioning ovaries and no documented
impairment of oviductal or uterine function that would cause sterility. This category
includes women with oligomenorrhoea (severe), women who are perimenopausal, and young
women who have begun to menstruate), has a negative serum pregnancy test at
screening, and agrees to one of the following where considered acceptable to the
local IRB/IEC: • Double-barrier contraception (condom with spermicidal jelly, foam
suppository, or film; diaphragm with spermicide; or male condom and diaphragm). •
Abstinence from sexual intercourse from 2 weeks prior to administration of the
investigational product, throughout the active study treatment period.

8. (Continued from above) • Male partner who is sterile prior to the female subject's
entry into the study and is the sole sexual partner for that female subject. • Any
intrauterine device (IUD). • Barrier methods including diaphragm or condom with a
spermicide.

9. Able to swallow and retain oral medication.

10. ECOG (Eastern Cooperative Oncology Group) performance status 0 to 2.

11. Serum creatinine < 1.4 mg/dL or calculated creatinine clearance (CrCl) >/= 60 mL/min

12. Aspartate and alanine transaminase (AST or ALT) reference range.

13. Patients must have a baseline ECG with QTc within the normal range within 28 days
prior to registration.

14. Total bilirubin
Exclusion Criteria:

1. Uncontrolled angina, congestive heart failure, MI (within last 6 months), congenital
long QT syndrome, history of clinically significant ventricular arrhythmia, prolonged
QTc interval on pre-entry EKG (greater than normal range)

2. Has evidence of recurrent or metastatic (Stage IV) breast cancer.

3. Is a pregnant or lactating female.

4. Has a known immediate or delayed hypersensitivity reaction or idiosyncrasy to
dasatinib

5. Has received treatment with any investigational drug in the previous 4 weeks.

6. Has received chemotherapy, immunotherapy, biologic therapy or endocrine therapy
within the past 12 weeks.

7. Contraindication to RPFNA including breast implant(s), bilateral radiation,
anticoagulation.

8. Unwillingness to undergo RPFNA.

9. Is considered medically unfit for the study by the investigator as a result of the
medical interview, physical exam, or screening investigations.

10. Is currently receiving oral steroid treatment (inhaled steroids are permitted)

11. Oral estrogen, progesterone, testosterone therapy within last 3 months.

12. Concurrent medical condition that would increase drug toxicity: Pleural or
pericardial effusion, coagulation or platelet function disorder, ongoing or recent
(less than 3 months gastrointestinal bleeding)

13. Hypokalemia or hypomagnesemia if it cannot be corrected

14. Concomitant Medications, consider the following prohibitions (Drugs must be
discontinued for 7 days prior to starting protocol therapy): Drugs that are generally
accepted to have a risk of causing Torsades de Pointes including : quinidine,
procainamide, disopyramide, amiodarone, sotalol, ibutilide, dofetilide erythromycins,
clarithromycin, chlorpromazine, haloperidol, mesoridazine, thioridazine, pimozide,
cisapride, bepridil, droperidol, methadone, arsenic, chloroquine, domperidone,
halofantrine, levomethadyl, pentamidine, sparfloxacin, lidoflazine. The concomitant
use of H2 blockers or proton pump inhibitors with dasatinib is not recommended. The
use of antacids should be considered in place of H2 blockers or proton pump
inhibitors in patients receiving dasatinib therapy. Patient agrees to discontinue St.
Johns Wort while receiving dasatinib therapy

15. Patient may not be receiving any prohibited CYP3A4 inhibitors