■ New diagnosis of DCIS without invasive breast cancer

■ Unilateral, bilateral, unifocal, or multifocal DCIS

■ A patient who has had a lumpectomy with positive margins as part of their treatment for a current DCIS diagnosis is eligible

■ No previous history of breast cancer (DCIS or invasive cancer) in either breast prior to current DCIS diagnosis

■ 40 years of age or older at the time of DCIS diagnosis

■ ECOG performance status 0 or 1

■ No contraindication for surgery

■ Baseline imaging:

○ Unilateral DCIS:

■ Contralateral normal mammogram ≤ 6 months of registration and ipsilateral breast imaging ≤ 120 days of registration

○ Bilateral DCIS:

■ Bilateral breast imaging ≤ 120 days of registration

■ Pathological criteria:

○ ADH suspicious for DCIS

○ Any grade I or grade II DCIS

○ Absence of invasive or microinvasive breast cancer

○ Diagnosis confirmed on core needle, vacuum-assisted biopsy or surgery ≤ 120 days of registration

○ ER(+) and/or PR(+) by IHC (≥10% staining or Allred score ≥ 4)

○ HER2 0, 1+ or 2+ by IHC if HER2 testing is performed

■ Histology slides reviewed and agreement between two clinical pathologists that pathology fulfills COMET eligibility criteria

■ At least two sites of biopsy for those cases where mammographic extent of calcifications exceeds 4 cm, with second biopsy benign or both sites fulfilling pathology eligibility criteria

■ Amenable to follow-up examinations

Ability to read, understand and evaluate study materials and willingness to sign a written informed consent document in Spanish or English