Inclusion Criteria

The patients enrolled into the study will include patients who meet the following
criteria:

Cohort 1: IO clinic breast cancer patients

1. Confirmed breast cancer of primary breast cancer with ICD9 code of 174.x, 233.0 or
V10.3

2. Female

3. ≥18 years of age

4. Can provide signed informed consent

5. 1st IO clinic visit ≤3 months prior to enrollment

6. Can read and understand the questionnaires

Cohort 1A: Sub-cohort of IO clinic patients (cases) who meet the following additional
criteria and for whom matched controls have been found from the CSS database.

1. ICD9 code of 174.x or 233.0

2. Diagnosis ≤2 years prior to 1st IO clinic visit

3. Minimum of two IO clinic visits within 7 months of enrollment

4. Provided Baseline Questionnaire

Cohort 2: Matched controls from CSS database for Cohort 1A patients

1. Confirmed breast cancer

2. Female

3. ≥ 18 years of age

4. Matches a patient in the 1A cohort for age at diagnosis (within 2 years), stage at
diagnosis, and time since diagnosis (within 6 months)

5. Can provide informed consent

6. Can read and understand the questionnaires