This is a prospective, non-interventional (observational) cohort study conducted within the medical network of the participating investigators and institutions. Patients meeting the eligibility criteria (see below) will be eligible for participation and the investigators will obtain written informed consent. A central Institutional Review Board (IRB), WCG IRB, will approve the protocol and each participating institution.

After a diagnosis of DCIS, the most representative tissue block (or 10 sections mounted on charged slides cut at 3-4 microns) will be sent to PreludeDx for DCISionRT. The most representative specimen should be selected from tissue collected via direct tumor biopsy (either core needle or excisional biopsy) as part of routine patient care. Patients must be enrolled in the study and the enrollment and pre-testing data forms must be completed and submitted before the DCISionRT results are reported. Then, after review of the DCISionRT results, the investigators complete and submit the post-testing data form. The patient may then be followed for up to 10 years (or until death) with completion of 5- and 10-year follow-up forms.

All study data will be stored in an encrypted, HIPAA-compliant database maintained by the coordinating center. Each consented patient will be assigned a unique Study ID number. Study personnel at each institution will maintain an electronic key to link the Study IDs of its own patients to the patients' local medical record number. All personal health information (PHI) will remain at the local institution and only de-identified data will be uploaded to the national registry. No genetic test results that may be used to identify the patient will be included in the database.

This study is designed to assess the magnitude of and conditions impacting physician treatment recommendations based on the DCISionRT test results, assessing patient preference, and within various clinicopathologic subgroups. This will also be the largest prospective determination of IBR outcomes with DCISionRT test result correlates to date.

Part I of the PREDICT Registry recently completed enrollment of 2,500 subjects for whom DCISionRT results had been reported using the original test protocol that classified patients into two risk groups, Low Risk and Elevated Risk.64

Part II of the PREDICT Registry will enroll up to an additional 3,000 subjects from 15 to 30 sites within the United States with each site enrolling between 100 and 300 patients. DCISionRT results will be reported using the updated test protocol that classifies patients into three risk groups, Low Risk, Elevated Risk and Residual Risk. Part II study procedures will be conducted exactly the same as Part I, except that further patient demographics and treatment preference, treatment recommendation details, and patient upstaging will be collected. Additional questions will be asked to determine how physicians use the Residual Risk group classification to make treatment decisions. De-identified imaging data may also be collected, and de-identified patient tissue samples may be collected after 1 year.

Inclusion criteria

1. Patient must have histologically confirmed ductal carcinoma in situ (DCIS) in a single breast (presence of lobular carcinoma in situ (LCIS) or other benign breast disease in addition to DCIS is acceptable).
2. Patient must have the DCISionRT test ordered during routine patient care.
3. Patient must be eligible for or have recently completed breast conserving surgery.
4. Patient must be eligible to receive radiation and/or systemic treatment.
5. Patient must be 30 to 85 years old.
6. Patient must have tumor size of less than 6 cm.
7. Patient must have been diagnosed with DCIS within 120 days of consent.

Exclusion criteria

1. Patient tissue is insufficient to generate DCISionRT test results or required DCISionRT inputs (age, tumor size, margin status, palpability) are missing.
2. Patient has evidence of invasive breast cancer, including microinvasion, lymph node involvement, or Paget's disease of the nipple or suspicious mammogram findings in the lymph nodes or contralateral breast.
3. Patient has been surgically treated with an ipsilateral mastectomy for primary DCIS.
4. Patient has had any prior ipsilateral or contralateral breast DCIS or invasive breast cancer.
5. Patient has a prior history of in-field radiation in the ipsilateral breast.
6. Patient has had prior systemic endocrine or chemotherapy prior to testing.
7. Patient is pregnant.

The study population will be selected from the clinical practices of the participating investigators and institutions. Patients who have been recently diagnosed with DCIS and are being evaluated for the need for further therapy will be screened for eligibility per the following eligibility criteria. Female patients 30 to 85 years with histologically confirmed ductal carcinoma in situ (DCIS) in a single breast of size less than 6 cm without evidence of invasive or microinvasive cancer and clinically eligible to receive breast-conserving surgery with or without radiation therapy.