Abstract PS13-05: A phase 2 study of oral paclitaxel and encequidar (oPac+E) in the treatment of cutnaeous angiosarcoma: The breast angiosarcoma subgroup

Background Cutaneous angiosarcomas are highly aggressive malignant tumors with poor prognosis. Currently there is no FDA-approved treatment. oPac+E is a combination of oral paclitaxel and a novel oral P-glycoprotein inhibitor, Encequidar. Materials and Methods: This is a phase-2 study evaluating the activity, safety and tolerability of oPac 205mg/m2 + E 12.9 mg once daily for 3 consecutive days weekly for patients with unresectable cutaneous angiosarcoma. Tumour response was evaluated every 6 weeks using RECIST and photography. Results: From Aug-2018 to May-2020, 7 of 26 enrolled patients (pts) had breast cutaneous angiosarcoma. All had previous breast cancer, mastectomy and radiotherapy and/or adjuvant chemotherapy, no prior taxane for angiosacoma and no metastatic disease. Median age was 66 yrs (range 49-76). Best objective response rates were: complete response (CR) 43% (3/7 pts), partial response (PR) 14% (1/7 pts), stable disease (SD) 43% (3/7 pts), progressive disease (PD) 0%. Furthermore, 3 pts (43%) who had inoperable lesions were deemed operable after Oraxol treatment and received curative intent surgical resection. Median progression free survival (PFS) was 17 weeks. oPac+E was generally well tolerated. Grade-3 treatment related adverse events (AEs) occurred in 5 pts: diarrhea=1, fatigue=2, neutropenia =1, dyspnea=1, dehydration=1, pneumonitis=1. Grade-4 AE were neutropenia in 2 pts. Grade-2 paraesthesia=1. All pts fully recovered. Dose reductions were needed in 3 subjects. No patients discontinued treatment due to AEs. To date no patients died. Conclusions: oPac+E may provide an effective oral treatment for radiation-associated breast angiosarcoma, with a high clinical benefit rate (CR + PR+ SD=100%), durable response and enabled resection of unresectable tumors. It is generally well tolerated even in elderly patients; with low incidence of neuropathy. It may allow patients to avoid hospital IV chemotherapy visits and the option of home treatment. Citation Format: Vinod Ravi, Michael Wagner, Tom Wei-Wu Chen, Herbert H Loong, Robert Mennel, Cheuh-Chuan Yen, Glen Clack, David Cutler, Rudolf Kwan, Wing=Kai CHan. A phase 2 study of oral paclitaxel and encequidar (oPac+E) in the treatment of cutnaeous angiosarcoma: The breast angiosarcoma subgroup [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS13-05.