DCIS: RECAST Trial Ductal Carcinoma In Situ: Re-Evaluating Conditions for Active Surveillance Suitability as Treatment

Inclusion Criteria: A. Female, at least 18 years old B. Previous diagnosis of HR+ DCIS (at least 50% ER or PR; biopsy will have been performed previously at diagnosis) with or without microinvasion * Patients with a diagnosis of hormone positive DCIS who have undergone surgery with positive margins that have not been re-excised are candidates to enroll in the trial. C. Patients who have previously received endocrine therapy should have a washout period of at minimum 4-6 weeks prior to the screening MRI on the RECAST-DCIS trial D. Bilateral mammogram performed within up to 6 months (180 days) of the start of trial treatment may be used for screening evaluation. If a bilateral mammogram has been performed within 1 year (12 months) of the start of trial treatment, then a diagnostic unilateral mammogram within 6 months (180 days) of the start of trial treatment will be acceptable for screening evaluation. E. MRI performed on an I SPY (RECAST) approved scanner within 2 months (60 days) of the start of trial treatment for lesion evaluation may be used for screening evaluation. F. CBC w/ diff, CMP, and Lipid Panel within normal limits within a year of the start of trial treatment. Abnormal labs to be repeated within 60 days prior to the start of trial treatment. Patients will be considered eligible for screening labs that are abnormal or out-of-range if the investigator has deemed the lab results not-clinically significant G. Negative urine or serum pregnancy test within 1 m…