Personalized Therapy for Breast Cancer: How Long More to be There?

Half a century ago, when the American Societyof Clinical Oncology (ASCO) was founded in۱۹۶۴, breast cancer was treated based on theHalstedian hypothesis of extensive surgery forlocoregional control as well as distant metastasisprevention. Over the last fifty years, the treatment ۱approaches toward this morbid disease hastransformed enormously. This revolution is ۲mostly the result of a greater understanding of thebiology of breast cancer as well as thedevelopment of targeted therapies. Today, variousmolecular subtypes of breast cancer have beenidentified, and the respective clinical course andresponse to existing therapeutic regimens havebeen widely studied. Nevertheless, the great ۳majority of patients in the world do not have accessto genetic assays. Estrogen receptor (ER),progesterone receptor (PR), HER۲, and Ki۶۷instead are routinely used for clinical-pathologicalclassification in order to choose the appropriateregimen for neo- or adjuvant therapies.۴ER-targeted therapies are among the greatesttherapeutic developments in the past ۵۰ years. Thekey change in ASCO guidelines (۲۰۱۴) isextending adjuvant endocrine therapy fordurations of up to ۱۰ years rather than ۵ years forhormone receptor positive breast cancer patientsfor risk reduction of recurrence and contralateralbreast cancer. Switching from tamoxifen to ۵aromatase inhibitor is based on menstrual status aswell as tolerance to either of the treatments. Itshould be kept in mind that additional informationis still needed regarding the identification ofpredicting markers for recurrence and improvedsurvival for this group of patients. Clinical trialssuch as TAILORx, and the RxPONDER, haveapplied Oncotype DX® genomic assays in orderto identify ER-positive patients for whomendocrine therapy alone is enough. As mentioned ۶,۷earlier, genetic assays are only available for a verylimited number of patients in the world, so doesn'tit mean that in routine clinical practice we are yetfollowing one-size-fits-all adjuvant endocrinetherapy?