This is a single-arm Phase 2 interventional treatment study to investigate changes in tissue lipidomes with omega-3 polyunsaturated fatty acids (PUFA) supplementation and correlations with pathological response in patients with early-stage breast cancer. Patients will be treated with a dietary supplement enriched with omega-3 PUFA (O3Supp) for 4 to 28 weeks prior to surgical resection of a breast tumor(s). Concurrent standard-of-care neoadjuvant treatment with clinically indicated systemic agents (such as chemotherapy, endocrine therapy, anti-HER2 therapy, immunotherapy) is allowed.