Chemotherapy With or Without Trastuzumab After Surgery in Treating Women With Invasive Breast Cancer

PRIMARY OBJECTIVES: I. To determine whether the addition of trastuzumab to chemotherapy (TC or AC→WP) improves invasive disease-free survival (IDFS) in women with resected node-positive or high-risk node-negative breast cancer which is reported as human epidermal growth factor receptor (HER)2-low by all HER2 testing performed. SECONDARY OBJECTIVES: I. To determine whether the addition of trastuzumab to chemotherapy (TC or AC→WP) improves disease-free survival (DFS)-ductal carcinoma in situ (DCIS) in women with resected node-positive or high-risk node-negative breast cancer which is reported as HER2-low by all HER2 testing performed. II. To determine whether the addition of trastuzumab to chemotherapy (TC or AC→WP) improves breast cancer-free survival (BCFS) in women with resected node-positive or high-risk node-negative breast cancer which is reported as HER2-low by all HER2 testing performed. III. To determine whether the addition of trastuzumab to chemotherapy (TC or AC→WP) improves recurrence-free interval (RFI) in women with resected node-positive or high-risk node-negative breast cancer which is reported as HER2-low by all HER2 testing performed. IV. To determine whether the addition of trastuzumab to chemotherapy (TC or AC→WP) improves distant recurrence-free interval (DRFI) in women with resected node-positive or high-risk node-negative breast cancer which is reported as HER2-low by all HER2 testing performed. V. To determine whether the addition of trastuzumab to chemotherapy (TC or AC→WP) improves overall survival (OS) in women with resected node-positive or high-risk node-negative breast cancer which is reported as HER2-low by all HER2 testing performed. VI. To evaluate the associations between amenorrhea and circulating reproductive hormone levels, and the associations between chemotherapy regimen, amenorrhea, and IDFS benefit in premenopausal women eligible at baseline for the menstrual history assessments. VII. To evaluate the toxicity associated with each of the regimens. VIII. To test the hypothesis that the HER2 messenger ribonucleic acid (mRNA) level is the predictor of the degree of benefit from trastuzumab and the threshold for benefit in the adjuvant setting is lower than defined by current American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) Guidelines for HER2 assays (immunohistochemistry \[IHC\] and fluorescent in situ hybridization \[FISH\]). IX. To identify and/or validate molecular predictors of the degree of benefit from the addition of trastuzumab to chemotherapy (TC or AC→WP). X. To test the alternative hypothesis that the main determinant of trastuzumab response in the adjuvant setting of HER2-low breast cancer is through antibody-dependent cellular cytotoxicity (ADCC) by demonstrating that the polymorphism of the Fcgamma receptor gene is predictive of the degree of benefit from the addition of trastuzumab to chemotherapy (TC or AC→WP). XI. To examine the relationship between behavioral host factors (obesity, tobacco, alcohol) and comorbid conditions that may influence systemic inflammation and breast cancer outcomes, controlling for tumor/stage characteristics and treatment assignment. XII. To examine the relationship between medication exposures that may influence systemic inflammation and breast cancer outcomes, controlling for tumor/stage characteristics and treatment assignment. XIII. To examine the relationship between comorbid conditions, medication exposures, and behavioral host factors together and breast cancer outcomes, controlling for tumor/stage characteristics and treatment assignment. OUTLINE: Patients are randomized to 1 of 2 treatment arms. NOTE: \*Chemotherapy regimen is based on the investigator's preference. ARM I: GROUP IA: Patients receive docetaxel intravenously (IV) over 60 minutes and cyclophosphamide IV over 30 minutes on day 1. Treatment repeats every 3 weeks for 6 cycles in the absence of disease progression or unacceptable toxicity. GROUP IB: Patients receive doxorubicin hydrochloride IV over 15 minutes and cyclophosphamide IV over 30 minutes on day 1. Treatment repeats every 2 or 3 weeks for 4 cycles in the absence of disease progression or unacceptable toxicity. Beginning 2-3 weeks after last dose of doxorubicin hydrochloride and cyclophosphamide, patients also receive paclitaxel IV over 60 minutes once weekly for 12 doses in the absence of disease progression or unacceptable toxicity. ARM II: GROUP IIA: Patients receive docetaxel and cyclophosphamide as in Group IA. Patients also receive trastuzumab IV over 30-90 minutes on day 1. Courses repeat every 3 weeks for 1 year in the absence of disease progression or unacceptable toxicity. GROUP IIB: Patients receive doxorubicin hydrochloride, cyclophosphamide, and paclitaxel as in Group IB. Patients also receive trastuzumab IV over 30-90 minutes weekly for 12 doses and then every 3 weeks for subsequent doses. Treatment repeats every 3 weeks for 1 year in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up every 6 months for 5 years and then every 12 months for 5 years.