Abstract

3132 Background: Despite progress in the development of HIPEC protocols for the treatment of peritoneal carcinomatosis, agent selection remains largely empiric with few biomarkers for guiding treatment. Ex vivo assessment of drug response using single-cell mass measurements offers a promising option for therapy selection. Previously, we have shown that mass response testing (MRT) is a malignancy- and drug-agnostic means of assessing drug response (1) and can predict a patient’s clinical response to therapy in a range of solid and hematological malignancies (2). Methods: Tissue specimens were collected from patients with peritoneal carcinomatosis as part of an ancillary study for a HIPEC clinical trial (NCT04847063) to explore the feasibility of performing MRT with these specimen types. Briefly, after overnight shipment of viable tumor tissue, tumor cells were isolated and treated with various therapies ex vivo. Single-cell mass distributions of vehicle and drug-treated populations were compared to determine the functional activity of each agent. Results: MRT was attempted for 60 patients with metastatic disease, 10 of whom had peritoneal carcinomatosis and ultimately received HIPEC. The HIPEC cases included histologies such as peritoneal mesothelioma (n=4), colorectal cancer (n=3), ovarian cancer (n=2), and small bowel adenocarcinoma (n=1). In total, 8 out of 10 peritoneal specimens had a sufficiently high tumor cell count, viability, and purity to perform MRT. These specimens displayed clear and statistically distinguishable mass response patterns of response and non-response to several different agents commonly used for HIPEC treatment such as cisplatin, oxaliplatin, doxorubicin, and mitomycin C. Study design:These feasibility results serve as the foundational data for launching a single-site phase II interventional study at the NCI’s Center for Cancer Research. The study will evaluate the potential benefit of personalized treatment regimens determined by MRT for patients with peritoneal carcinomatosis, particularly mesothelioma, a context where therapeutic options have relative equipoise in clinical efficacy. Tumor biopsies will be obtained via laparoscopy prior to HIPEC and submitted to a CLIA-certified lab for MRT to assess the responses of various clinically acceptable agents. The HIPEC regimen will be selected based on these MRT results returned within two days of sample collection. Enrolled patients will then undergo cytoreduction and HIPEC, and progression-free and overall survival will be monitored. As a single-arm, non-randomized trial, patient responses will be compared with a matched synthetic control to assess the impact of MRT on efficacy of HIPEC regimens. Conclusions: MRT is feasible for peritoneal carcinomatosis tissues, with future studies focusing on its role in guiding HIPEC treatment. 1. Nat Comm Bio,2022. 2. JCO PO, 2024. Clinical trial information: NCT04847063 .