APPLICATION OF LAPATINIB IN PATIENTS WITH HER-2 POSITIVE METASTATIC BREAST CANCER

Abstract

Relevance.  Initially,  HER2-positive  breast  cancer  was  one  of  the  most 
aggressive types of this disease, which was characterized by a very rapid tumor growth 
rate,  a  high  risk  of  disease  relapse  and  the  appearance  of  distant  metastases.  In 
developed countries, in the structure of cancer incidence in women, breast cancer (BC) 
ranks 1st or 2nd (20–25% of all cancer cases). More than half of patients with breast 
cancer develop distant metastases at one stage or another of the disease. Metastatic 
breast cancer (mBC ) is an incurable disease, but modern treatment approaches allow 
achieving  clinically  significant  results.  The  identification  of  more  and  more  new 
molecular genetic and immunohistochemical markers and their correlations makes it 
possible to individualize treatment tactics for patients [1]. The most significant factors 
for poor prognosis in mBC include overexpression of HER2, a transmembrane receptor 
with tyrosine kinase activity, which is the result of amplification of the HER2 gene on 
chromosome 17 [2,3,11]. Studies have shown that the HER2-positive subtype is more 
common among young women with advanced stages of the disease, is characterized by 
high aggression and rapid dissemination of the tumor process, and does not depend on 
the  size  of  the  tumor.  Even  with  minimal  carcinoma  sizes  and  in  the  absence  of 
involvement  of  regional  lymph  nodes,  HER2  overexpression  is  associated  with  an 
unfavorable course of the disease [3, 4]. Today, determination of HER2 status in breast 
cancer is mandatory for all stages of the disease; it is necessary to assess the prognosis 
and develop an optimal treatment algorithm. Determination of HER2 status in a tumor 
is  standardized  and  is  performed  on  paraffin  blocks  of  the  tumor  using 
immunohistochemical analysis and, in case of questionable analysis results (HER2-
2+), is supplemented by determining gene  amplification using in hybridization situ 
(ISH) [5–7]. Anti-HER2 therapy is currently the standard approach to the treatment of 
breast  cancer  patients  with  HER2  overexpression  or  HER2  gene  amplification  and 
usually  complements  chemotherapy  or  hormonal  therapy  [14,15].  Lapatinib  is  an 
antibody-drug conjugate that delivers the latter directly to HER2-positive cancer cells, 
thereby limiting damage to healthy tissue [8,9,12]. The use of Lapatinib can increase 
efficacy and achieve tumor control in young patients with HER-2 positive mBC .