* At increased risk of developing breast cancer, due to at least one of the following risk factors:

* Gail score ≥ 1.66
* Age ≥ 60 years
* Prior atypical ductal hyperplasia, lobular hyperplasia, or lobular carcinoma in situ on breast biopsy
* Prior ductal carcinoma in situ (DCIS) treated with total mastectomy with or without tamoxifen (tamoxifen must have been completed ≥ 3 months prior to randomization)
* No prior DCIS treated with lumpectomy with or without radiation
* No prior invasive breast cancer
* Not BRCA1 or BRCA2 carriers

PATIENT CHARACTERISTICS:

Previous:

* 35 and over
* Female
* Postmenopausal, defined as one of the following:

* over 50 years of age with no spontaneous menses for at least 12 months before study entry
* 50 years of age or under with no menses (spontaneous or secondary to hysterectomy) for at least 12 months before study entry AND with follicle-stimulating hormone level within postmenopausal range
* Underwent prior bilateral oophorectomy
* No other malignancies within the past 5 years except adequately treated nonmelanoma skin cancer, curatively treated carcinoma in situ of the cervix, or other curatively treated solid tumors with no evidence of disease for ≥ 5 years
* No uncontrolled hypothyroidism or hyperthyroidism
* No major medical or psychiatric illness (including substance and alcohol abuse within the past 2 years) that would preclude study participation or compliance
* Must be accessible for treatment and follow-up
* Willing to complete quality of life questionnaires in either English or French

Current: MAP.3 participants who were randomized to the exemestane arm, are currently receiving exemestane as part of the MAP.3 study and who have not completed 5 years of exemestane.

OR MAP.3 study participants who were randomized to the placebo arm and who have either completed 5 years of study drug or who are still receiving placebo. Note: this applies only to centres that choose to allow placebo "cross-over".

PRIOR CONCURRENT THERAPY:

Previous:

* More than 3 months since prior and no concurrent hormone replacement therapies
* More than 3 months since systemic estrogenic, androgenic, or progestational agents
* More than 3 months since prior and no concurrent hormonal therapies, including, but not limited to the following:

* Luteinizing-hormone releasing-hormone analogs (e.g., goserelin or leuprolide)
* Progestogens (e.g., megestrol)
* Prolactin inhibitors (e.g., bromocriptine)
* Antiandrogens (e.g., cyproterone acetate)
* Selective estrogen-receptor modulators (e.g., tamoxifen, toremifene, or raloxifene)
* No investigational drug within 30 days or 5 half lives prior to randomization
* No concurrent endocrine therapy
* No concurrent estrogens, androgens, or progesterones
* Concurrent low dose (≤ 100 mg/day) prophylactic aspirin allowed
* Concurrent bisphosphonates for prevention or treatment of osteoporosis allowed
* No other concurrent medications that may have an effect on study endpoints

Current: There are no prior concurrent therapy restrictions for the amended MAP.3 study.