Abstract 291P
Background
Trastuzumab emtansine (TDM1) is indicated for the treatment of metastatic HER2-positive breast cancer (HMBC) after progression on prior trastuzumab and taxane (TT). There are few data on its efficacy after pertuzumab, trastuzumab and taxane (PTT). The present study is a regional multicenter retrospective evaluation of the activity of TDM-1 after front line pertuzumab based therapy.
Methods
All three oncology centers of “Region de Murcia” participated in a restrospective observational study. Patients diagnosed with HMBC treated with a minimum of 2 cycles of TDM1 after PTT were included. Efficacy and safety were analysed and compared with TH3RESA and EMILIA study.
Results
Between Feb 2015 until Apr 2020, 52 patients with HMBC were treated with TDM1 after PTT. After a median of follow-up of 33 months, 8 patients were still under TDM1 therapy and 30 patients (58%) have died at the end of the study. Median progression free survival (PFS) was 8,4 months (95% IC 6,9 – 9,9) and median overal survival (OS) was 23,6 months (95% IC 17,5 – 29,7). Overall Rate Response (ORR) was 42%. The most frequent grade 3 toxicity was thrombocytopenia (8%) (see table). No dose-limiting cardiotoxicity was seen. Table: 291P
| Th3resa Study | EMILIA Study | TDM1RM Study | |
| N | 404 | 495 | 52 |
| Age (median, range) | 53 (27-89) | 53 (25-84) | 50 (29-75) |
| ECOG – % 0 1 2 | 45 50 5 | 60 39 | 15 61 23 |
| Hormone-receptor – % HR+ HR- | 51 46 | 57 41 | 64 35 |
| Visceral disease – % | 75 | 67 | 79 |
| Previously brain metastasis – % | 10 | 9 | 38 |
| Prior chemotherapy regimens – % 0 or 1 >1 | (≤ 3 regimens) 33 (> 3) 67 | 61 39 | 81 19 |
| ORR – no. (%) | 108 (31) | 173 (44) | 22 (42) |
| Median duration of response – median (95% IC) | 9,7 (6,6-10,5) | 12,6 (8,4 – 20,8) | 9,7 (6,6 – 12,8) |
| PFS (median, 95% IC) | 6,2 (5,6 – 6,9) | 9,6 | 8,4 (6,9 – 9,9) |
| OS (median, 95% IC) | 22,7 (19,4 – 27,5) | 30,9 | 23,6 (17,5 – 29,7) |
| Dose reduction - % | 9 | 16 | 25 |
| Grade 3 toxicity – no. (%) Astenia Anemia Thrombopenia Neutropenia | 4 (1) 14 (4) 24 (6) 10 (3) | 12 (2) 13 (3) 63 (13) 10 (2) | 2 (4) 1 (2) 4 (8) 2 (4) |
Conclusions
T-DM1 was an effective and well-tolerated treatment in routine clinical practice in patients with HMBC after PTT. ORR, PFS and OS were similar than pivotal study after only trastuzumab-taxane. We observed a similar toxicity of TDM1. We had a higher incidence of brain metastases.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.