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

OBJECTIVES:

Primary

- Compare the disease-free survival (DFS) of postmenopausal women treated with continuous
letrozole for 5 years vs intermittent letrozole over a 5-year period.

Secondary

- Compare overall survival of patients treated with these two regimens.

- Compare distant DFS of these patients.

- Compare breast cancer-free interval of these patients.

- Compare sites of first DFS failure in these patients.

- Compare second (nonbreast) malignancies in these patients.

- Compare deaths without prior cancer events in these patients.

- Compare adverse events resulting from these two regimens.

OUTLINE: This is a multicenter study. Patients are stratified according to treatment center
and type of prior endocrine therapy (selective estrogen receptor modulators [SERMs] alone vs
aromatase inhibitors [AIs] alone vs both SERMs and AIs each for at least 1 month). Patients
are randomized to 1 of 2 treatment arms.

- Arm I: Patients receive oral letrozole daily for 5 years.

- Arm II: Patients receive oral letrozole daily for the first 9 months of years 1 through
4, followed by 12 months in year 5.

After completion of study therapy, patients are followed annually.

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