Primary Objective:

(i) To identify panels of RNAs and proteins predictive of response to HER2 targeted agents, considering clinical responses. (ii) To investigate associations between presence vs. absence (or relative levels) of identified extracellular (EC) RNAs/proteins and patients' clinicopathological characteristics, including age at diagnosis, time to progression and overall survival, as well as correlations with serum protein biomarkers routinely analysed for these patients. (iii) To compare HER2 positive samples versus HER2 negative samples for the existence of RNAs/proteins identified in (i) and (ii).

Secondary Objective:

To develop a predictive model for use in the HER2 positive population based on the most accurate and sensitive combination of the identified biomarkers.

This is a translational pilot study, involving two patient cohorts, designed to identify predictive biomarkers for HER2 targeted therapy, which will be validated in a larger future study.

Cohort 1: 300 newly diagnosed (including metastatic) HER2 positive breast cancer patients. Cohort 2: 30 newly diagnosed HER2 negative breast cancer patients.

Blood specimens will be taken:

• before starting treatment (cohort 1 and 2)
• after receiving chemotherapy and before starting HER2 targeted treatment (if applicable) (cohort 1)
• within one month following 1st treatment of HER2 targeted treatment (cohort 1)
• approximately every 3 months (coinciding with formal disease assessment) while on HER2 targeted treatment for a maximum of 5 years (cohort 1)

Blood will be processed to serum, which will be analysed for RNA and protein biomarkers.

Inclusion Criteria:

1. Patient with a newly diagnosed (including metastatic) HER2 positive breast cancer, who is to commence HER2 targeted treatment.

   OR

   - Patient with a newly diagnosed HER2 negative breast cancer, who is to commence any type of treatment.

2. Patient must be female and aged 18 years or over.

3. Patient must provide written informed consent.

Exclusion Criteria:

1. Patients who do not fulfil the inclusion criteria mentioned above

• HER2 positive breast cancer:Female patients with newly diagnosed (including metastatic) HER2 positive breast cancer.
• HER2 negative breast cancer:Female patients with newly diagnosed HER2 negative breast cancer.