Inclusion Criteria:

          -  Patients must have received prior unilateral breast radiotherapy (RT) for ductal
             breast carcinoma in situ (DCIS) or invasive cancer (>= 12 weeks after the end of RT),
             and have an intact unradiated (non-RT) breast.

               -  Note: The upper limit for interval since RT will be 5 years, since oral endocrine
                  therapy (OET) for DCIS is usually administered during the 5 years that follow the
                  end of RT.

          -  Eastern Cooperative Oncology Group (ECOG) performance status =< 1 (Karnofsky >= 70%).

          -  No history of coagulopathy, or daily use of aspirin/nonsteroidal antiinflammatory
             drugs (NSAIDs).

          -  A prior history of malignancy is allowed, as long as the patient is considered to have
             ?no evaluable disease? and cancer treatment has been completed.

          -  Females of child-bearing potential (FOCBP) and male partners of female participants
             must agree to use TWO effective forms of birth control (abstinence is not an allowed
             method) prior to study entry and for the duration of study participation, and for two
             months following the last dose of study medications. Effective birth control methods
             are: copper IUD (intrauterine device), diaphragm/cervical cap/shield, spermicide,
             contraceptive sponge, condoms. Should a female patient become pregnant or suspect she
             is pregnant while participating in this study, she should inform her treating
             physician immediately.

               -  NOTE: A FOCBP is any woman (regardless of sexual orientation, having undergone a
                  tubal ligation, or remaining celibate by choice) who meets the following
                  criteria:

                    -  Has not undergone a hysterectomy or bilateral oophorectomy

                    -  Has had menses at any time in the preceding 12 consecutive months (and
                       therefore has not been naturally postmenopausal for > 12 months).

          -  FOCBP must have a negative urine pregnancy test within 7 days prior to registration on
             study.

          -  Willingness to avoid exposing breast skin to natural or artificial sunlight (i.e.
             tanning beds) for the duration of the study drug use.

          -  Patients must have the ability to understand and the willingness to sign a written
             informed consent prior to registration on study.

        Exclusion Criteria:

          -  Patients receiving any other investigational agents within 30 days of registration are
             not eligible.

          -  Patients currently using oral selective estrogen receptor modulators (SERMS)
             (tamoxifen, raloxifene, bazedoxifene) are not eligible.

               -  Note: Prior or current endocrine therapy other than SERMs are allowed.

          -  Patients who have a history of allergic reactions attributed to compounds of similar
             chemical or biologic composition afimoxifene (4-OHT) are not eligible.

          -  Patients who have an uncontrolled intercurrent illness including, but not limited to
             any of the following, are not eligible:

               -  Hypertension that is not controlled on medication

               -  Ongoing or active infection requiring systemic treatment

               -  Symptomatic congestive heart failure

               -  Unstable angina pectoris

               -  Cardiac arrhythmia

               -  Psychiatric illness/social situations that would limit compliance with study
                  requirements

               -  Any other illness or condition that the treating investigator feels would
                  interfere with study compliance or would compromise the patient?s safety or study
                  endpoints.

          -  Female patients who are pregnant or nursing are not eligible.

          -  Patients with prior bilateral breast cancer radiotherapy or radiotherapy for lymphoma
             will be excluded.

          -  Patients with skin lesions on the breast that disrupt the stratum corneum (e.g.
             eczema, ulceration) are not eligible.

          -  Patients with a history of endometrial neoplasia are not eligible.

          -  Patients with a history of thromboembolic disease are not eligible.

               -  Note: history of varicose veins and superficial phlebitis is allowed.

          -  Patients who are undergoing active treatment for any malignancy will be excluded.

          -  Male patients are excluded from this study since there are no data regarding skin
             penetration of 4-OHT though male chest wall skin (which is thicker and hairier than
             female chest wall skin).