Assess the impact of dietary omega 3 free fatty acids and/or letrozole on obese, postmenopausal breast cancer patients.

Prospective, comparative, three arm, short term, non-interventional study with correlative biomarker endpoints. Sixty (60) obese (≥ 30 BMI) newly diagnosed ER+ postmenopausal breast cancer patients will be recruited to participate in a short term (30 day) Phase 0 biomarker evaluation study prior to surgical resection.

Inclusion Criteria:

• At least 18 years of age.
• Postmenopausal as confirmed in medical history
• Ability to understand the purposes and risks of the study and has signed a written informed consent form approved by the investigator's IRB (Institutional Review Board)/Ethics Committee.
• Estrogen receptor positive breast cancer. Body mass index of 30 or greater.
• Consented for tissue collection on CTRC (Cancer Therapy and Research Center) repository 07-32

Exclusion Criteria:

• Cachexia
• Active systemic illness (infection including viral illnesses such as Hepatitis and HIV)
• Chronic use of NSAIDs (nonsteroidal anti-inflammatory drugs) aspirin or omega-3 free fatty acid supplementation within the last 60 days (defined as greater than or equal to 7 consecutive days)
• Any NSAIDs aspirin or omega-3 free fatty acid supplementation within the last 14 days
• History of medical noncompliance
• Scheduled date of surgical resection that would limit the amount of time taking the intervention to less than 21 days