Toxicity, side effects, and unpredictable effectiveness have been the hallmarks of anti-cancer therapies used in the past to treat breast and other primary cancers. More recently, targeted therapies have been developed that reduce patient risk and provide remarkable improvement in patient outcomes.
"A predictive marker can be defined as a factor that indicates sensitivity or resistance to a specific treatment."* Not all cancers respond the same to a particular therapy; consequently, not all patients will be helped by the same therapy. Patient safety is enhanced when it can be determined prior to treatment whether the patient will benefit from the treatment. Utilization of predictive markers has improved patient quality of life and reduced morbidity and mortality.
