Significance of Patient-Reported Outcomes for Metastatic Breast Cancer Patients

<b><i>Background:</i></b> Breast cancer is still the most common malignancy in women worldwide. Once metastasized, breast cancer treatment primarily aims at reducing symptom burden, thereby trying to maintain and improve a patient’s quality of life (QoL), delaying disease progression, and prolonging survival. Curing the disease is not possible in the palliative setting. To better understand metastatic breast cancer patients, their symptoms, and wishes, which are important for treatment decision making and outcome, patient-reported outcomes (PROs) are of great importance, giving an impression of what really matters to and concerns a patient. <b><i>Summary:</i></b> Many advances have been made to implicate PROs in clinical trials, non-interventional studies, registries, and clinical routine care of metastatic breast cancer. For example, large phase III trials like PALOMA-3 (NCT01942135), MONALEESA-7 (NCT02278120), HER2CLIMB (NCT02614794), and KEYNOTE-119 (NCT02555657) trials implemented PROs in their trial design to assess the QoL of their trial patients. Also, non-interventional studies on metastatic breast cancer, e.g., the NABUCCO study (IOM-02240), and prospective non-interventional, multicenter registries, e.g., the tumor registry breast cancer (NCT01351584) or the breast cancer registry platform OPAL (NCT03417115), have implemented PROs to assess QoL during the anticancer treatment periods of the patients. <b><i>Key Message:</i></b> Using PROs in metastatic breast cancer can support shared treatment decision making and management of symptoms, eventually leading to an improvement in QoL. Progressively, regulatory authorities take PROs into consideration for the approval of new drugs. Hence, the implication of PROs in cancer treatment, and especially in MBC, is of significant value.