This study has two purposes. One is to determine if daily sulindac decreases breast density; a risk factor for breast cancer development. The second is to determine whether sulindac reduces pain and stiffness associated with regular use of aromatase inhibitors given for the treatment of breast cancer.

To accomplish our study aims, we will conduct a phase II, single are trial of sulindac in postmenopausal women with early stage ER+ breast cancer who are receiving an aromatase inhibitor as adjuvant hormonal therapy. Approximately 75 breast cancer patients, stable on AI therapy (minimum of 3 months) for the treatment of their breast cancer will receive sulindac 150 mg bid for 12 months. Breast imaging will be conducted at baseline, 6 and 12 months.

The primary endpoint of the study will be change in the appearance of the contralateral, uninvolved breast as measured by quantitative Fat Water Ratio (FWR-MRI) mapping at 12 months in response to sulindac therapy. As changes in breast density in the contralateral, uninvolved breast will be the primary endpoint of the study, patients with bilateral breast cancer or those patients undergoing bilateral mastectomies or reconstruction surgery will be ineligible. Secondary endpoints of the trial include 12 month change in general pain and joint specific stiffness and pain as assessed by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). A number of exploratory endpoints are planned and include comparison of MRI measures of the breast, tissue biomarkers, and pain at 6 months as early indicators of 12 month responses. For the tissue biomarkers, core needle biopsies will be obtained in a subset of women who consent to the procedure from the uninvolved contralateral breast at baseline and at 6 months. Tissue studies will include characterization of tissue histology (graded by cellularity and stromal elements) and molecular measures of proliferation and apoptosis.

Inclusion Criteria:

• Eligibility criteria will include: Postmenopausal women with of first incidence of early stage (stages 0 - III) hormone receptor positive breast cancer stabilized on anastrozole therapy for at least 3 months
• Patients must have started on anastrozole and plan to continue on anastrozole therapy for a minimum of 12 months
• Patients must have an unaffected, non-irradiated contralateral breast with a baseline breast density score of > 25% as measured by standard digital mammography (BIRADs score > 2) or magnetic resonance imaging (MRI) performed within 12 months of randomization to the study
• A willingness to follow the study protocol, as indicated by provision of informed consent to participate
• A willingness to avoid taking NSAIDs outside of the trial (rare NSAID use for musculoskeletal symptoms excepted)
• Normal renal function as determined by a serum creatinine < upper limit of normal
• No known contraindication to NSAID use
• Normotensive or controlled blood pressure (< 140/90) on a single anti-hypertensive medication

Exclusion Criteria:

• Current or anticipated need for daily aspirin or NSAID use including aspirin for cardiovascular protection
• Known intolerance to NSAIDs
• Age > 75 years
• History of cardiovascular disease including prior myocardial infarction, angina, stroke, or transient ischemic attack (TIA)
• Diabetes requiring drug therapy
• Current smoker
• History of Uncontrolled hypertension
• Blood pressure > 140/90 at baseline by home monitoring
• History of GI ulcers, chronic GERD, or GI bleeding in the past 5 years
• History of a bleeding diathesis or current anticoagulant therapy
• Daily therapy with H2 blockers or protein pump inhibitors
• History of claustrophobia
• Have electrically, magnetically, or mechanically activated implants including cardiac pacemaker, cochlear implants, magnetic surgical clips or prostheses.

For baseline analyses for the sulindac arm, we included only those participants who remained in the study after the NSAID washout and who started the intervention with sulindac (n=50). For the baseline analyses for the observation arm, we included those participants who either completed their baseline MRI and/or questionnaires for the secondary arthralgia endpoints (n=50).

Adverse event data were collected over 13 months.

Participants in the observation only group were not systematically followed for adverse events. There was not active intervention and there was not intent to compare the two groups.