OBJECTIVES: Utility values are a key component of economic evaluations and a stated requirement of reimbursement bodies when evaluating a new treatment. The current study estimated health-state utilities associated with metastatic breast cancer (mBC) and adverse events (AE) of potential new treatments from a societal perspective in the UK.  METHODS: In-depth telephone interviews were conducted in 2015 in the UK with 12 mBC patients (age≥60), 3 oncologists and 1 nurse practitioner to draft and validate health-state descriptions relevant to mBC patients.  Ten mBC health-states were developed to be further assessed in TTO interviews: stable disease, progressive disease, mood change/anxiety, rash, nausea/vomiting, fatigue, stomatitis, hyperglycemia, neutropenia, and elevated liver functioning. One hundred individuals from the UK were recruited to complete a socio-demographic form, EQ-5D and Time-trade-off (TTO) interviews where time (in years) was “traded” to avoid mBC health-states, thereby determining preferences for developed health-states. A mixed model was also developed to predict utility decrements for health-states and assess the impact of patient-level variables (eg age, gender) on predicted utilities. RESULTS: The predicted utility value for stable disease was 0.83 (CI: 0.79-0.86) based on mixed model analyses. The lowest predicted utility value was (0.39 [CI: 0.33-0.45]) for progressive disease.  Predicted utilities for other health states ranged from 0.77 (hyperglycemia [CI: 0.72-0.80]) to 0.46 (mood change/depression and fatigue [CI: 0.40-0.52]).  Further analyses revealed that age and gender did not significantly affect predicted utility values in mBC. CONCLUSIONS: The current study shows the impact of treatment-related AEs on patient’s HRQL. Health-state utility values in mBC were highest for stable disease followed by hyperglycemia.  Symptomatic side effects and progressive disease in mBC had the lowest values suggesting societal preference to avoid these AEs if possible.  Additional research is needed to further validate these findings.