Open-label, Single-arm, Multicenter Study to Evaluate the Rheumatological Tolerability of Letrozole as an Adjuvant Breast Cancer Treatment in Postmenopausal Women Who Are Intolerant and Discontinue Anastrozole Due to Grade 2-3 Arthralgia-myalgia

Inclusion Criteria:

1. Postmenopausal women with HR+ early stage breast cancer at the time of initial
diagnosis. For study purposes, postmenopausal is defined as:

- Age ≥ 50 y and amenorrheic for 12 or more months.

- Age ≥ 50 y and amenorrheic for 3 or more months after receiving adjuvant
chemotherapy.

- Age < 50 y and amenorrheic for 12 or more months.

- Prior bilateral oophorectomy.

- Prior hysterectomy and has postmenopausal levels of FSH, LH, and estradiol as
per local institutional standards.

- Age > 55 y and prior hysterectomy.

2. Patients who are intolerant and discontinue anastrozole 2-3 weeks prior to study
entry when given as adjuvant treatment for HR+ early stage breast cancer due to
grade 2-3 (NCI-CTCAE V3) arthralgia-myalgia.

3. Hormone receptor-positive tumors as defined by institutional standards.

4. ECOG performance status of 0, 1, or 2

5. Consent to participate in the trial. -

Exclusion Criteria:

1. Postmenopausal women with HR+ metastatic or locally relapsed breast cancer excluding
chest wall recurrence with no evidence of systemic disease.

2. Recent history of pain associated with non-traumatic bone fracture.

3. Pain requiring chronic use of analgesics (due to any reason).

4. History of rheumatological disease except osteoarthritis.

5. Prior hormonal therapy with AIs other than anastrozole.

6. Systemic hormone replacement therapy (HRT) less than 4 weeks before study entry other
than Estring®, Vagifem® or low dose estrogen vaginal cream.

7. Concomitant disease which significantly affects quality of life.

8. Patient unable to complete self administered questionnaire.

9. Patients unable to sign consent form.

Other protocol-defined inclusion/exclusion criteria may apply