Abstract P4-12-15: Long term outcome with trastuzumab in HER2-positive metastatic breast cancer: A retrospective analysis at The Royal Marsden Hospital, with a median 6 years follow up

Abstract

Abstract Background Trastuzumab is currently the standard of care in combination with chemotherapy for patients with early and advanced HER2 positive breast cancer. Some patients with advanced disease have long remissions, but published data on the efficacy and safety of long-term trastuzumab are limited. Patients and Methods We have retrospectively assessed efficacy and safety of trastuzumab on all patients with HER2 positive advanced breast cancer, who received first-line trastuzumab-containing therapy between 2001 and 2009 at a single institution, The Royal Marsden Hospital. Patients who received adjuvant trastuzumab were excluded. The primary endpoints of the study were time to disease progression and response duration. Secondary endpoints included overall response rate, overall survival and cardiac toxicity related to maintenance trastuzumab beyond 12 months. An exploratory analysis of factors predicting long disease remission on trastuzumab beyond 12 months was also performed. Results 192 patients with HER2 positive locally advanced/metastatic breast cancer treated with trastuzumab containing therapy as first line treatment were identified. The median age at start of treatment was 52 years. The main site of metastatic disease was visceral in 136 (71%) of patients, and 16 patients (8.5%) with central nervous system (CNS) involvement. 152 (79%) patients received trastuzumab in combination with chemotherapy. 18 patients (9%) received trastuzumab with endocrine therapy only. 22 (11%) patients received trastuzumab alone. The median time to progression was 45. weeks (95% CI: 38 – 52 weeks). The overall response rate (ORR) was 63%, including 14 patients (7%) with CR and 107 patients (56%) with PR. Overall disease control (CR+ PR+ SD for at least 6 months) was achieved in 169 (88%) patients. Patients who received trastuzumab with chemotherapy had superior response rate (71%) to trastuzumab alone or in combination with endocrine therapy (37% and 58% respectively). 125 patients (65%) were on trastuzumab for more than 1 year, 88 (46%) for more than 2 years, 63 (33%) for more than 3 years and 25 (13%) for 5 years or more. The median overall survival was 125 weeks, and 28% still alive at 5 years. At the time of the analysis with a median follow-up 6yrs, 46 patients (24%) were still alive. 23 of these (50%) had stopped trastuzumab after discussion. 38 patients (20%) had CNS relapse on trastuzumab, of which 19 (10%) relapsed in the brain alone. Maintenance trastuzumab therapy was well tolerated. 29 (15%) patients had any grade LV dysfunction during trastuzumab treatment, of which 11 (6%) stopped trastuzumab. No deaths or other serious side effects related to trastuzumab were observed. Conclusion Trastuzumab frequently achieves long term control of metastatic breast cancer with more than 25% of patients alive after 5 years. The optimal duration of therapy remains uncertain. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-12-15.