The widespread introduction of anti-HER2 agents has changed the natural course of Her2-positive breast cancer. The use of trastuzumab, and later dual anti-HER2 blockade with pertuzumab, in neoadjuvant regimens significantly increased the chances of complete cure. However, among patients with early and locally advanced forms of Her2-positive cancer, there is a cohort with an extremely unfavorable prognosis – tumors that have not achieved complete pathomorphological regression after neoadjuvant chemotherapy.The presence of a residual tumor in Her2-positive breast cancer has long been only a prognostically unfavorable factor without the potential to influence disease outcome. The results of the international phase III study KATHERINE, which demonstrated the high efficacy of post-adjuvant therapy with trastuzumab emtansine (T-DM1) in this patient cohort, have established a new standard of care. Due to T-DM1 adjuvant therapy, the possibility to significantly improve long-term results determined the predictive characteristics of the morphological response to the choice of treatment tactics, which became an important argument in favor of neoadjuvant therapy in patients with not only locally advanced but also primarily resectable Her2-positive breast cancer, followed by personalization of therapy.This article presents our own experience with post-neoadjuvant therapy with trastuzumab emtansine in a young patient with a residual tumor. The data of the main studies in early Her2-positive breast cancer are summarized.
Trastuzumab Mechanism of Action; 20 Years of Research to Unravel a Dilemma