Are there benefits in routine clinical practice of continuing trastuzumab after progression for metastatic breast cancer patients?

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