ADC vs HP dual-antibody for HER2-positive advanced breast cancer after failed to TKI

e13036 Background: The application of tyrosine kinase inhibitor (TKI) is higher than that of antibody-drug conjugate (ADC) in the second-line anti-HER2 targeted therapy of patients with advanced breast cancer in China. The purpose of this study is to explore the efficacy and safety of the new generation anti-HER2 ADC, the previous generation ADC(T-DM1) and HP dual-antibody (trastuzumab + pertuzumab) in patients with HER2 positive advanced breast cancer who failed TKI therapy. Methods: This is a retrospective, nonrandomized, controlled study to compare the regimen of the new generation ADC, HP dual-antibody and T-DM1 for patients who failed TKI treatment. The primary end point was progression-free survival (PFS). The secondary end points included the overall response rate (ORR), the clinical benefit rate (CBR) and the safety. Results: A total of 213 patients were enrolled from January 2013 to June 2022. All patients were from the department of oncology, the fifth medical center of Chinese PLA General Hospital. The median age of all patients was 47y. Among these patients,73 cases were in the new generation ADC group (including DS8201 30 cases, MRG002 24 cases, ARX788 10 cases and RC48 9 cases), 71 cases were in T-DM1 group and 69 cases were in HP group (combination chemotherapy including taxane, vinorelbine, gemcitabine and capecitabine). The median PFS of the patients in the new generation ADC group , HP group and T-DM1 group was 7.0m, 6.6m, 4.0m respectively. The difference between the new generation ADC group and T-DM1 group was significant (HR=0.44,95%CI 0.30-0.66, P<0.0001), which between HP group and T-DM1 group was also significant (HR=0.50,95%CI 0.34-0.74, P<0.0001), meanwhile, which between the new generation ADC group and HP group was not significantly (HR=0.88, 95%CI 0.58-1.32, P=0.527)(Figure 1). The ORR in three groups was 54.8%, 27.5%, 22.5% respectively, and the new generation ADC group was significantly higher than the other two groups (P<0.0001). The CBR in three groups was 65.8%, 62.3%, 47.9% respectively. The difference between the new generation ADC group and HP group was not significantly (P=0.67), and both were significantly higher than T-DM1 group (P=0.03). The most common grade 3 or 4 adverse event in the new generation ADC group was neutropenia (20.5%) and which in T-DM1 group was thrombocytopenia (28.1%). The incidence of interstitial lung disease in the two groups was 5.4% and 1.4% respectively. No grade 5 adverse event occurred. Conclusions: In our study, the new generation ADC significantly improved PFS and ORR compared with that for T-DM1 with manageable toxicity, so it can be considered an optimized subsequent treatment for HER2 positive advanced breast cancer after TKI failure. In addition, there was no significant difference in PFS and CBR between HP and the new generation ADC, thus HP dual-antibody regimen is also an optional treatment for patients who never used pertuzumab.