Do HER-2 positive metastatic breast cancer patients benefit from the use of trastuzumab beyond disease progression? A mono-institutional experience and systematic review of observational studies.

Though preclinical evidence supports the protracted use of trastuzumab to reach sustained anti-tumor activity, the activity of trastuzumab beyond disease progression remains controversial in HER-2 over-expressing (HER-2+) metastatic breast cancer (MBC) patients. We retrospectively evaluated a total of 59 patients with HER-2 + MBC treated at our institution with trastuzumab-based therapies. Our results were added to those obtained in similar observational studies and summary estimates for overall response (OR) and clinical benefit (CB) to first and second trastuzumab-based lines were calculated. In our series of patients we observed an OR of 59.3% and 27% for first and second trastuzumab-based lines, respectively, with a corresponding CB of 83% and 62.2%, respectively. Time to first and second progression were 9.5 months and 6.7 months, respectively. The combined analysis showed an OR of 50% for first trastuzumab-based regimen and 21.2% for second trastuzumab-based line. The corresponding values for CB were 77.6% and 42.6%, respectively. A second trastuzumab-containing regimen beyond progression yields a considerable rate of OR and CB in HER-2 + MBC patients. Randomized trials are warranted.