e12500 Background: Currently, there are no data related to re-administering trastuzumab (T) + pertuzumab (P) beyond the second-line therapy to patients with human epidermal growth factor receptor 2-positive advanced/metastatic breast cancer (HER2-MBC) who had previously received P. The present study targeted patients with HER2-MBC who were previously treated with P and aimed to evaluate the efficacy and safety of additional administration (top-up intervention) of P post-disease progression (PD) after standard treatment with T plus chemotherapy vinorerbine(VNR) or eribulin (ERI). Methods: SBP-08 was a multicenter, collaborative, single-arm phase II study of HER2-MBC patients who had previously received P. After standard treatment with T and chemotherapy, P was additionally administered (top-up intervention) post-PD. Results: Eleven HER2-MBC patients, recruited between June 2016 and June 2018, who had previously received P participated in this study. Their mean age was 63.5 years, and 45% were estrogen receptor (ER)-negative, while 55% were ER-positive. The mean chemotherapy history was 3.6 regimens, with a median of four regimens. Previous treatment regimens with P had been effective in all patients. All patients had organ metastasis and treatment histories with TDM-1. Initially, during the two-year case collection period, registration of 30 patients was planned. However, the study was terminated because the interim analysis did not demonstrative effectiveness, and it was decided that there were no potential benefits to the patients. The overall response rate (ORR) of the standard treatment was 0%, stable disease (SD) was 36%, PD was 55%, and the clinical benefit rate (CBR) was 0%. The following combination anticancer agents were used: VNR (10 patients) and ERI (one patient). The intervention treatment (top-up with P) achieved the following: ORR 0%, SD 22%, PD 78%, and CBR 0%. PFS for the standard treatment was 1.6 months, whereas PFS for the intervention treatment was 1.3 months. In the standard treatment, febrile neutropenia was observed in two patients. No increases in adverse events were observed with the intervention treatment. Conclusions: No clinical benefit was demonstrated with the intervention treatment in the present study. Top-up with P after standard treatment with T and chemotherapy post-PD was deemed ineffective. Clinical trial information: UMIN000020837.
PCN104 Cost-Utility MODEL of Trastuzumab Emtansine (T-DM1) in HER2-Positive, Unresectable, Locally Advanced or Metastatic Breast Cancer Previously Treated with Trastuzumab and a Taxane, Compared with Capecitabine PLUS Lapatinib, Trastuzumab PLUS Capecitabine and Capecitabine ALONE in Turkey