Prolonged survival of patients receiving trastuzumab beyond disease progression for HER2 overexpressing metastatic breast cancer (MBC)

Background: The aim of this retrospective analysis was to evaluate
the impact of trastuzumab-based regimens on the survival of
patients with HER2-overexpressing metastatic breast cancer (MBC).
The study specifically focussed on the influence of the
continuation of trastuzumab-based treatment despite tumor
progression on survival. Patients and Methods: Patients with HER2
overexpressing MBC were included in this retrospective analysis.
HER2 overexpression was determined by the immunohistochemical
staining score (DAKO Hercep Test (TM)). Trastuzumab was applied at
a loading dose of 4 mg/kg and a maintenance dose of 2 mg/kg.
Results: Among 136 HER2 overexpressing patients (DAKO score 3+), 66
patients received first-line trastuzumab, 47 patients received
trastuzumab as second-line therapy and 23 patients received
trastuzumab beyond disease progression. There was no significant
difference regarding the duration of trastuzumab-based treatment
(first-line: 29.5 weeks vs. second-line: 25 weeks). Moreover, there
was no difference in the response rate (first-line: 37.9% vs.
second-line: 35.7%) or the median survival (p = 0.47 log rank).
Patients who received >= 2 trastuzumab-based regimens for MBC
survived significantly longer compared to those who had received
only 1 regimen (>= 2 regimens: 62.4 months vs. 1 regimen: 38.5
months; p = 0.01 log rank). Conclusions: Trastuzumab is highly
effective in the treatment of HER2 overexpressing MBC. Compared to
historical controls, overall survival appears to be markedly
prolonged, particularly in patients who received sequential
trastuzumab-based treatment beyond disease progression.