Letrozole in Preventing Cancer in Postmenopausal Women Who Have Received 4-6 Years of Hormone Therapy for Hormone Receptor-Positive, Lymph Node-Positive, Early-Stage Breast Cancer

DISEASE CHARACTERISTICS:

* Confirmed diagnosis of prior operable, noninflammatory breast cancer meeting the following criteria:

  * Steroid hormone receptor-positive tumors (estrogen receptor and/or progesterone receptor), determined by immunohistochemistry, after primary surgery and before commencement of prior endocrine therapy
  * Prior local treatment including surgery with or without radiotherapy for primary breast cancer with no known clinical residual loco-regional disease
  * Following primary surgery, eligible patients must have had evidence of lymph node involvement either in the axillary or internal mammary nodes, but not supraclavicular nodes
  * Clinically disease-free
* Must have completed 4-6 years of prior adjuvant selective estrogen receptor modulators (SERMs), aromatase inhibitors (AIs), or a sequential combination of both

  * When calculating 4-6 years, neoadjuvant endocrine therapy should not be included
* No evidence of recurrent disease or distant metastatic disease
* No prior bilateral breast cancer

PATIENT CHARACTERISTICS:

* Female
* Must be postmenopausal by any of the following criteria:

  * Patients of any age who have had a bilateral oophorectomy (including radiation castration AND amenorrheic for \> 3 months)
  * Patients 56 years old or older with any evidence of ovarian function must have biochemical evidence of definite postmenopausal status (defined as estradiol, luteinizing hormone \[LH\], and follicle-stimulating hormone \[FSH\] in the postmenopausal range)
  * Patients 55 years old or younger must have biochemical evidence of definite postmenopausal status (defined as estradiol, LH, and FSH in the postmenopausal range)

    * Patients who have received prior luteinizing-hormone releasing-hormone (LHRH) analogues within the last year are eligible if they have definite evidence of postmenopausal status as defined above
* Clinically adequate hepatic function
* No bone fracture due to osteoporosis at any time during the 4-6 years of prior therapy
* No prior or current malignancy except adequately treated basal cell or squamous cell carcinoma of the skin, in situ carcinoma of the cervix or bladder, or contra- or ipsilateral in situ breast carcinoma
* No other nonmalignant systemic diseases (cardiovascular, renal, lung, etc.) that would prevent prolonged follow-up
* No psychiatric, addictive, or any other disorder that compromises compliance with protocol requirements

PRIOR CONCURRENT THERAPY:

* See Disease Characteristics
* More than 12 months since prior and no other concurrent endocrine SERM/AI therapy
* Any type of prior adjuvant therapy allowed including, but not limited to, any of the following:

  * Neoadjuvant chemotherapy
  * Neoadjuvant endocrine therapy
  * Adjuvant chemotherapy
  * Trastuzumab (Herceptin®)
  * Ovarian ablation
  * Gonadotropin releasing hormone analogues
  * Lapatinib ditosylate
* No concurrent hormone-replacement therapy, bisphosphonates (except for treatment of bone loss), or any other investigational agent