Phase II/III study of paclitaxel/carboplatin alone or combined with either trastuzumab and hyaluronidase-oysk or pertuzumab, trastuzumab, and hyaluronidase-zzxf in HER2 positive, stage I-IV endometrial serous carcinoma or carcinosarcoma (NRG-GY026).

Abstract

TPS5641 Background: Uterine serous carcinoma and uterine carcinosarcoma are rare, high-risk uterine cancer subtypes that overexpress HER2 in up to 40% and 10% of cases, respectively. Phase II data demonstrated a benefit in adding trastuzumab in HER2 positive advanced and recurrent uterine serous carcinoma. Dual anti-HER2 therapy has the potential for further improvement in survival. Methods: This is a non-blinded, three-arm randomized phase II/III study. The primary objective is to evaluate the efficacy of trastuzumab and hyaluronidase-oysk (HERCEPTIN HYLECTA) or a fixed dose combination of pertuzumab, trastuzumab, and hyaluronidase-zzxf (PHESGO) in combination with paclitaxel/carboplatin in patients with HER2 positive uterine serous carcinoma or carcinosarcoma. The primary outcome of the phase II component is PFS. Depending on the phase II results, the study will progress to a phase III study of either two or three study arms. Patients in the control arm (Arm 1) receive carboplatin and paclitaxel every 3 weeks for 6 cycles. Patients on Arm 2 receive carboplatin and paclitaxel with trastuzumab and hyaluronidase-oysk every 3 weeks for 6 cycles plus one year of maintenance trastuzumab and hyaluronidase-oysk. Patients enrolled on Arm 3 receive carboplatin and paclitaxel with trastuzumab, pertuzumab, and hyaluronidase-zzxf every 3 weeks for 6 cycles plus one year of maintenance trastuzumab, pertuzumab, and hyaluronidase-zzxf . Those with an ongoing partial response may continue maintenance therapy for up to three years. Patients are eligible if they are diagnosed with chemo-naïve, non-recurrent stage IA-IVB myoinvasive uterine serous or carcinosarcoma. All tumors must be HER2 positive as defined by the ASCO/CAP Breast Cancer 2018 guidelines (testing performed locally). Tumors may also be HER2 positive based on next generation sequencing testing. Patients may have measurable, non-measurable, or no measurable disease and may have a plan for vaginal brachytherapy . Key exclusion criteria include severe heart disease or interstitial lung disease. The phase II portion of this study is open and enrolling. Clinical trial information: NCT05256225 .