The Effects of HER2 Receptor Signaling on Human Brown Fat Activity

General inclusion criteria: * Female * Age \> 18 years * Histologically confirmed breast cancer * No prior neoadjuvant treatment * Estrogen receptor positive (\>1%) * Presence of cold activated brown fat as evidenced by a change in Δtemp. of \>1°C (post cooling - precooling temperature). HER2 positive group: HER2-positive (HER2+) and Estrogen receptor-positive (ER+) breast cancer patients (N = 15): * HER2 positive breast cancer as defined by ASCO/CAP criteria * Scheduled to receive adjuvant chemotherapy, a total of 17 series of trastuzumab and endocrine treatment Control group: HER2-negative breast cancer patients (HER2-) and Estrogen receptor-positive (ER+) breast cancer patients (N = 15): * HER2 negative breast cancer as defined by ASCO/CAP criteria * Scheduled to receive adjuvant chemotherapy and endocrine treatment Exclusion Criteria: * Any other cancer (excluding carcinoma in situ and radically operated localised squamous skin cancer) with clinical activity within the last 2 years * Metastatic breast cancer * Metabolic diseases such as diabetes (exceptions can be made if the disease is well treated, assessed by the clinically responsible medical doctor (see section 18)) * Regular use of prednisolone - use in relation to chemotherapy only is ok * Pregnancy * Untreated or dysregulated hypertension defined as outpatient clinic systolic BP \> 155 and diastolic BP \> 95 * Clinically significant ventricular or atrial arrhythmia * Untreated coronary artery disease or angina pectoris * Symptomatic heart failure (NYHA ≥ 2) * Known cold urticaria