Table 1

Eligibility criteria for the COMET trial

Inclusion criteria	Exclusion criteria
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 fulfils 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	All grade III DCIS Male DCIS Concurrent diagnosis of invasive or microinvasive breast cancer in either breast prior to randomisation Documented mass on examination or imaging at the site of DCIS prior to biopsy yielding diagnosis of DCIS Bloody nipple discharge or skin changes associated with DCIS Mammographic finding of BI-RADS 4 or greater within 6 months of registration at site other than that of known DCIS, without pathological assessment 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 in last 6 months

Inclusion criteria

Exclusion criteria

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 fulfils 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

All grade III DCIS
Male DCIS
Concurrent diagnosis of invasive or microinvasive breast cancer in either breast prior to randomisation
Documented mass on examination or imaging at the site of DCIS prior to biopsy yielding diagnosis of DCIS
Bloody nipple discharge or skin changes associated with DCIS
Mammographic finding of BI-RADS 4 or greater within 6 months of registration at site other than that of known DCIS, without pathological assessment
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 in last 6 months

ADH, atypical ductal hyperplasia; BI-RADS, Breast Imaging Reporting and Data System; COMET, Comparison of Operative versus Monitoring and Endocrine Therapy; DCIS, ductal carcinoma in situ; ECOG, Eastern Cooperative Oncology Group; ER(+), oestrogen receptor positive; HER2, human epidermal growth factor 2; IHC, immunohistochemistry; PR(+), progesterone receptor positive.