National Surgical Adjuvant Study of Breast Cancer 06

INTERVENTION: Compare the case of postoperative treatment with chemotherapy followed by endocrine therapy (Letrozole administration) (CL group) and endocrine therapy (letrozole administration) alone (L group) in a randomized comparison study. CONDITION: breast cancer ; breast cancer PRIMARY OUTCOME: Disease‐free survival SECONDARY OUTCOME: Percentage of patients clinically responding to neoadjuvant LET therapy Histological tumor response to neoadjuvant LET therapy Percentage of patients undergoing breast‐preserving surgery,; Overallsurvival(OS),; DFS/OS in subgroups of patients according to clinical response (CR, PR, SD or PD) to neoadjuvant LET therapy Safety,; health‐related quality of life(HRQOL) and Economic Evaluation of Drugs INCLUSION CRITERIA: [Primary enrollment] Those who meet all of the following requirements will be considered for admission: 1) Postmenopausal women with histologically diagnosed primary invasive breast cancer. A woman will be considered postmenopausal if she: (1)Is 60 years old or older, (2)Is under 60 years of age and had her last menstrual period more than 1 year ago (and if she has not undergone hysterectomy), and/or (3)Has undergone bilateral ovariectomy. Even if the above criteria cannot clarify the menopausal status, a woman will be considered postmenopausal if she has postmenopausal plasma levels of FSH (e.g., >=30 mIU/mL) and estradiol (e.g., <10 pg/mL) designated at each center. 2)T1c‐T2,N0,M0 carcinoma according to the TNM classification 3)Positivity for estrogen receptor ( >=10% cells stained in an immunohistochemical [IHC] assay) in a pretreatment needle biopsy specimen 4)Negativity for HER2 (2+ or a worse rating in an IHC assay or a negative