1656 - The efficacy of eribulin mesylate with trastuzumab for locally advanced or metastatic HER2-positive breast cancer treated with prior pertuzumab and/or T-DM1: results from a Phase II, single arm, multicenter study (N-SOG 10 study). (101P)

Background

Eribulin mesylate (ERI) demonstrated a survival benefit in patients with locally recurrent or metastatic breast cancer who previously received 2 or more chemotherapy regimens. Recently, we conducted Phase II study about the efficacy of ERI with trastuzumab (ERI+TRA) as late-line therapy for locally advanced or metastatic HER2-positive breast cancer (UMIN000012350), and reported that objective response rate (ORR) and median progression-free survival (mPFS) were 17% and 4.6 months. However, some patients who received prior pertuzumab (PER) and/or T-DM1 were enrolled in that study, there are limited data on the efficacy of ERI+TRA in those patients. The aim of this study was to assess the efficacy of this combination therapy based on prior PER and/or T-DM1 use.

Methods

In primary phase II study, patients with locally advanced or metastatic HER2 positive breast cancer who previously received at least one chemotherapeutic regimen, received ERI at 1.4 mg/m² intravenously (I.V.) on days 1 and 8 of each 21-day cycle with an initial TRA dose of 8 mg/kg I.V. on day 1, followed by 6 mg/kg of TRA on day 1 of each subsequent cycle. ORR, clinical benefit rate (CBR) and PFS were assessed in patients who had and had not received prior PER and/or T-DM1.

Results

Thirty-six patients (median age: 60.5 years) received ERI+TRA. 69.4% (n = 25) had previously treated with prior PER and/or T-DM1, defined as ‘prior’ patients. Remaining 30.6% (n = 11) without both agents were defined as ‘non-prior’ patients. In prior patients compared with non-prior patients, median number of prior treatment regimens was 4 (range, 1‐8) versus 3 (range, 1-7), respectively; ORR was 12.0% versus 27.3%, respectively; CBR was 24.0% versus 54.5%, respectively; mPFS was 4.3 versus 9.7 months, respectively.

Conclusions

ERI+TRA demonstrated lower efficacy than in non-prior patients, but CBR and PFS were 24.0% and 4.3 months, which was considered to be a clinically relevant treatment option in patients who received prior PER and/or T-DM1.

Clinical trial identification

UMIN000012350.

Legal entity responsible for the study

Nagoya Surgical Oncology Group

Funding

Eisai

Disclosure

All authors have declared no conflicts of interest.