• The primary endpoint of efficacy is the proportion of the patients who have detectable circulating tumor cells (CTC) after completion of study (at the time of either resuming systemic treatment of breast cancer or unacceptable toxicity being observed). [ Time Frame: Approximately 3 years. ] [ Designated as safety issue: Yes ]
  

All patients will have medical history, physical exam, and standard labs at baseline, including platelets, AST/ALT, creatinine, PT/PTT. Platelet function, CTC tests, and Urine Ntx will be taken at baseline, two weeks, and then monthly. Patients may remain on study until treating physician elects to resume systemic therapy. If patients continue on study after one month, they will receive physical exam, medical history/progress notes, standard labs, platelet function (at the treating physician's discretion), and CTC tests on a monthly (q 4 week) schedule or every 3 weeks if receiving trastuzumab or other i.v. medication that necessitates returning to the clinic on an every 3 week schedule.

Plavix/Aspirin Arm

Patients will receive a 300 mg loading dose of Plavix on day 1, followed by 75 mg/day, and aspirin 81 mg per day starting day 1. Treatment will be continued until the treating physician elects to resume systemic therapy for the treatment of breast cancer or until unacceptable toxicity is observed. A pill diary will be collected monthly to monitor patients' compliance with the medication regimen.

No Treatment Arm

Patients randomized to the no treatment arm will receive no anti-platelet drugs but will be monitored by the treating physician. Assessment of performance status, quality of life, CTC, and platelet function will be performed. Patients will continue on the study until the treating physician elects to resume systemic therapy for the treatment of breast cancer, or until unacceptable toxicity is observed. Patients will be followed for 6 months maximum as part of the protocol.