Study Of MK-0752 In Combination With Tamoxifen Or Letrozole to Treat Early Stage Breast Cancer

Inclusion Criteria: * Patients must have histologically or cytologically confirmed early stage, ER-positive (Allred score ≥3), invasive breast cancer that is not either locally advanced by criteria other than size or inflammatory, and is not metastatic. - Patients must be candidates for surgical removal of the tumor by lumpectomy or mastectomy. * Patients must not have bilateral tumors. Tumor must be amenable to core biopsy in midstudy. * Patients must be \>18 years of age. * Patients must have a performance status ≤1 by Zubrod criteria. * Patients must have a life expectancy of greater than three months. * Patients must have normal organ and marrow function within 28 days of registration as defined below: * absolute neutrophil count \>1,500/μL * platelets \>100,000/μL * total bilirubin ≤1.5 x the institutional upper limit of normal * AST(SGOT)/ALT(SGPT) \<2 X institutional upper limit of normal * creatinine within normal institutional limits OR * creatinine clearance \>60 mL/min/1.73 m2 for patients with creatinine levels above institutional normal * Women of child-bearing potential must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation. A negative serum pregnancy test must be obtained within 72 hours of receiving the first dose of the hormonal therapy as well as within 72 hours of the first dose of the MK-0752 GSI medication for women of child-bearing potential. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately. Exclusion Criteria: * Patients may not have received any prior chemotherapy or endocrine therapy (tamoxifen, raloxifene, or an aromatase inhibitor) and may not have received prior therapy with a gamma-secretase inhibitor or other investigational agents. - Patients may not have received previous radiation therapy. * Patients may not be currently participating or have participated in a study with an investigational compound or device within 30 days. * Patients must not have known brain or CNS disease, evidence of brain or CNS metastases, or carcinomatous meningitis. * Patients must not have an uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements. * Patients may not have known hypersensitivity to the components of MK-0752 or it analogs. * Patients will be excluded if there is a known history of human immunodeficiency (HIV) virus infection, or a known history of hepatitis B or C infection. * Patients must not have a previous history of inflammatory bowel disease or uncontrolled irritable bowel syndrome. * Patients must not have a history of greater than one basal cell carcinoma of the skin within the past five years or a history of Gorlin syndrome.