Disclosed are methods and topical formulations for treating and/or preventing cell proliferative diseases and disorders including breast cancer and ductal carcinoma is situ (DCIS) using local transdermal therapy (LTT). The disclosed methods typically include administering topically to the breast or breasts of the patient a topical formulation comprising an effective dose of the tamoxifen metabolite, N-desmethyl-4-hydroxytamoxifen (i.e., endoxifen or ENX) for treating breast cancer. The topical formulation may be described as a transdermal formulation and the topical formulation may comprise, consist essentially of, or consist of endoxifen as an active ingredient.