Overdiagnosis and overtreatment resulting from mammographic screening have been estimated to be as high as 1 in 4 patients diagnosed with breast cancer although the absence of standard definitions for measuring overdiagnosis has led to much uncertainty around this estimate. The national health care expenditure resulting from false positive mammograms and breast cancer overdiagnosis has been estimated to approach $4 billion annually. There is general consensus that much of this burden derives from the treatment of DCIS; for those estimated 40,000 women per year whose DCIS may never have progressed even without treatment, medical intervention can only harm. In those women who undergo surgical management of DCIS, there is risk of developing persistent pain at the surgical site, with estimates ranging from 25-68%. Importantly, persistent pain after lumpectomy may be as prevalent as that after total mastectomy. Persistent postsurgical pain is rated by patients as the most troubling symptom, leading to disability and psychological distress, and is often resistant to management. Although prospective population-based data have demonstrated significant patient and surgical focus on pain with remarkably high levels of chronic pain 4 and 9 months after breast surgery, much of these data have been collected in women with invasive cancer, with little data directly relevant to patients with DCIS.

The overarching hypothesis of the study is that management of low-risk DCIS using an active surveillance (AS) approach does not yield inferior cancer or quality of life outcomes compared to guideline concordant care (GCC).

Inclusion Criteria:

• New diagnosis of DCIS without invasive cancer. Unilateral, bilateral, unifocal, or multifocal DCIS will be eligible, provided that all DCIS meets eligibility criteria
• No prior history of breast cancer in either breast
• Age ≥ 40 at time of DCIS diagnosis
• Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1
• No contraindication for surgery
• Pathologic diagnosis of DCIS within 90 days of registration:
  • Histology slides reviewed and diagnosis confirmed by concordance among two clinical pathologists
  • Grade I/II DCIS without invasion or microinvasion
  • Diagnosis confirmed on core needle biopsy or surgical biopsy within 90 days of registration
  • Estrogen Receptor (ER)(+) and/or Progesterone Receptor (PR)(+) by ImmunoHistoChemistry (IHC) (≥ 10% staining or Allred score ≥ 4)
  • Human Epidermal Growth Factor Receptor 2 (HER2) 0, 1+, or 2+ by IHC if HER2 testing is performed
  • Absence of comedo necrosis
• Required initial laboratory values:
  • Absolute Neutrophil Count (ANC) ≥ 1,000/ul
  • platelet count ≥ 100,000/ul
  • serum creatinine ≤ 1.7 mg/dL
  • serum glucose ≤ 2.5 x Upper Limit of Normal (ULN)
  • serum estradiol assay < 20 pg/ml (required for patients <55 years of age and *less than one year of amenorrhea)
• At least two sites of biopsy for those cases where mammographic extent of calcifications exceeds 4 cm, both sites fulfilling eligibility criteria for DCIS without invasion or microinvasion
• Amenable to follow up examinations
• Ability to read, understand and evaluate study materials and willingness to sign a written informed consent document
• Reads and speaks Spanish or English, or availability of an appropriate professional interpreter at enrollment

Exclusion Criteria:

• Male DCIS
• Previous or concurrent diagnosis of invasive breast cancer, including microinvasion
• Mass on examination or imaging at site of DCIS prior to biopsy yielding diagnosis of DCIS
• Bloody nipple discharge
• Mammographic finding of Breast Imaging Reporting and Data System (BIRADS) 4 or greater at site other than that of known DCIS within 6 months of registration
• Use of investigational cancer agents within 6 weeks prior to diagnosis
• Any serious and/or unstable pre-existing medical, psychiatric, or other existing condition that would prevent compliance with the trial or consent process
• Pregnancy
• Documented history of prior tamoxifen, aromatase inhibitor or raloxifene