Abstract
HER2 overexpression is present in 15-25% of breast cancers and is related to specific biologic features and treatment response,constituting a strong predictive factor. Targeted anti-HER2 therapy has improved significantly the prognosis of patients withthis type of tumor and is a standard component of all adjuvant, neoadjuvant and palliative treatment regimens, except for verysmall tumors of the earliest stages (pT1a pN0).
HER2-targeting agents belong to two different groups: monoclonal antibodiesand tyrosine kinase inhibitors. They are combined with chemotherapy - mostly taxanes, and/or hormonal therapy, or may becombined together; this dual HER2 inhibition often shows better effect than single anti-HER2 therapy.
There are, however, manyquestions to be addressed in the HER2-positive breast cancer management: other factors influencing the response to anti-HER2therapy (histological subtype, hormonal receptor status, mutations of PIK3CA, PTEN genes), timing of HER2-targeted therapywithin the combined treatment regimens (concurrent versus sequential application), duration of anti-HER2 therapy (particularlyin adjuvant settings), combinations with other treatment (combinations of several anti-HER2 agents, combinations with othertargeted therapy), etc. A number of studies involving many of these issues are ongoing; their results are expected to improvefurther the management and survival of HER2-positive breast cancer patients.