The efficacy of trastuzumab beyond metastatic disease progression (PD) is controversial. We retrospectively analyzed 213 patients with HER2-positive metastatic breast cancer treated with trastuzumab-based therapies between November 1998 and December 2010. Out of 213 patients, 134 (58%) had received trastuzumab consecutively for at least 1 year and 154 of 213 patients (67%) had received two or more lines of consecutive trastuzumab-based therapy beyond PD. For these subgroups of patients, we examined the correlation between patients' survival and time to first tumor progression (TTP). Among 134 patients who received trastuzumab for at least 1 year, 66 (49%) never had PD within the first year of treatment, whereas 68 (51%) had PD at least once within the first year. The estimated 2-year overall survival (OS) after 1 year was 82% for those who had no PD during the first year (median OS 5.1 years) and 70% for those who had PD (median OS 2.6 years) (P<0.0001). Among 154 patients who received two or more lines of consecutive trastuzumab-based therapy beyond PD, we calculated a median first TTP of 8.7 months. In terms of survival after first progression, patients with a longer first TTP (≥8.7 months) had better survival compared with those who had a shorter first TTP (39 months, 95% CI 31-63; vs. 28 months, 95% CI 22-32; P=0.0004). T-based therapy was well tolerated and only five patients experienced a cardiac event. Our retrospective data suggest that treatment with trastuzumab beyond progression is a viable option for patients with advanced HER2-positive breast cancer, whose disease has progressed on previous trastuzumab-based regimens.