The key goal in the treatment of metastatic breast cancer is to prolong survival, with an emphasis on restricting treatment-related toxicity as much as possible. Despite the plethora of treatment modalities available in metastatic breast cancer, significant survival differences are relatively uncommon. Symptom relief and quality of life are other important, clinically validated measurement instruments. Symptom relief in particular is not used as widely used as it could be, in contrast to lung cancer where it has been proven clinically informative. Finally, time to disease progression is an increasingly used primary endpoint in comparing treatments for metastatic breast cancer; this measure includes both patients who achieve an objective response, and those whose disease may be stabilized with treatment.