Letrozole in Breast Cancer Who Have Received 5 Years of Aromatase Inhibitor Therapy

DISEASE CHARACTERISTICS:

* Previously diagnosed with primary breast cancer
* Must have received 4½ - 6 years of aromatase inhibitor therapy (e.g., letrozole, anastrozole, or exemestane), either as initial therapy or after prior tamoxifen citrate, including treatment received as part of clinical trial CAN-NCIC-MA17

  * Completed aromatase inhibitor therapy ≤ 2 years ago
* No metastatic or recurrent disease, contralateral breast cancer, or ductal carcinoma in situ in either breast, as determined by the following:

  * Clinical examination of the breast area, axillae, and neck within the past 60 days
  * Mammogram within the past 12 months\*
  * Chest x-ray within the past 60 days
  * Bone scan, if alkaline phosphatase \> 2 times normal and/or there are symptoms of metastatic disease AND confirmatory x-ray, if bone scan results are questionable, within the past 60 days
  * Abdominal ultrasound, liver scan, or CT scan of the abdomen within the past 60 days, if ALT, AST, or alkaline phosphatase \> 2 times normal NOTE: \*A baseline mammogram is not required for patients who have undergone bilateral complete mastectomy
* Hormone-receptor status:

  * Estrogen receptor positive (ER+) and/or progesterone receptor positive (PR+) primary tumor at the time of diagnosis, defined as a tumor receptor content of \> 10 fmol/mg protein or receptor positive by immunocytochemical assay (for patients not previously enrolled on clinical trial CAN-NCIC-MA17)
  * ER+ and/or PR+ primary tumor OR hormone receptor status of primary tumor unknown (for patients previously enrolled on clinical trial CAN-NCIC-MA17)

PATIENT CHARACTERISTICS:

* Menopausal status not specified
* ECOG performance status 0-2
* Life expectancy ≥ 5 years
* WBC \> 3.0 x 10\^9/L OR granulocyte count (polymorphs + bands) ≥ 1.5 times 10\^9/L
* Platelet count \> 100 x 10\^9/L
* AST and/or ALT \< 2 times upper limit of normal (ULN)\*
* Alkaline phosphatase \< 2 times ULN\*
* Able (i.e. sufficiently fluent) and willing to complete quality-of-life questionnaires in either English or French (NCIC CTG participating centers)

  * Inability to complete questionnaires due to illiteracy in English or French, loss of sight, or other equivalent reason allowed
* Accessible for treatment and follow-up
* No other prior or concurrent malignancy except adequately treated, superficial squamous cell or basal cell skin cancer, carcinoma in situ of the cervix, or other cancer treated \> 5 years ago that is presumed cured NOTE: \*Elevated levels allowed provided imaging examinations have ruled out metastatic disease

PRIOR CONCURRENT THERAPY:

* See Disease Characteristics
* No concurrent selective estrogen receptor modulator (e.g., raloxifene, idoxifene)
* No other concurrent anticancer therapy