BP13. Phase II Trial of Systemic Therapy Plus Intraperitoneal (IP) Paclitaxel (PTX) in Gastric/GEJ Cancer Peritoneal Carcinomatosis (GPC)- STOPGAP Trial

Friday, March 6, 2026

1:02 PM - 1:09 PM MST

Location: 301A

Co-Author(s)

LA

Luisa M. Aguilar, MS

University of California Irvine
Orange, California, United States
Shishir K. Maithel, MD, FACS, FSSO

Professor of Surgery
NorthWestern University
Chicago, Illinois, United States
NU

Nataliya V. Uboha, MD, PhD

Associate professor of surgery
University of Wisconsin
Madison, Wisconsin, United States
TT

Thomas H. Taylor, PhD (he/him/his)

Principal Statistician
University of California Irvine
Irvine, California, United States
KN

Kristen Neumann, DNP

Nurse Practitioner
University of California
Orange, California, United States
MO

Michael P. O'Leary, MD

Assistant Professor of Surgery
University of California, Irvine
Orange, California, United States
Oliver S. Eng, MD (he/him/his)

Associate Professor of Surgery
University of California, Irvine
Orange, California, United States
AC

April Choi, MD (she/her/hers)

Assistant Professor of Medicine
University of California Irvine
Orange, California, United States
FD

Farshid Dayyani, MD, Phd

University of California Irvine
Orange, California, United States

Primary Presenter(s)

Maheswari Senthil, MD, FACS, FSSO (she/her/hers)

Professor of Surgery
University of California Irvine
Irvine, California, United States

Slides

Introduction

Peritoneal carcinomatosis (PC) is a common and deadly metastasis in gastric cancer. Systemic therapy alone may not adequately treat PC due to limited perfusion across peritoneum as result of blood-peritoneal barrier. Hence, combining intraperitoneal (IP) chemotherapy with systemic therapy is a viable alternate strategy to treat PC. We sought to evaluate the safety, feasibility, and preliminary efficacy of iterative normothermic IP PTX plus systemic therapy as consolidation strategy during first-line treatment.

Methods

STOPGAP is a single center, single arm, open label phase II trial. Patients (pts) with histology proven gastric/GEJ (Siewert 3) adenocarcinoma with peritoneal involvement and no evidence of visceral metastasis who had no evidence of disease progression after 3-6 months of systemic treatment were eligible. After diagnostic laparoscopy (diag lap), and IP port placement, pts were treated with IP PTX 40 mg/m2 plus IV PTX 50 mg/m2, leucovorin 20 mg/m2 and 5-fluorouracil 400 mg/m2 (bolus) on days1 and 8, every 21 days for 4 cycles. If indicated, anti-PD1 antibody +/- trastuzumab were continued as before enrollment. Pts without progression after 4 cycles underwent repeat diag lap. Pts with peritoneal cancer index (PCI) £10 were considered for cytoreduction (CRS) with heated IP chemotherapy (HIPEC). IP PTX was discontinued after CRS. The primary endpoints were safety and feasibility and 12-months progression free survival (PFS12); secondary endpoints included overall survival (OS) and patient-reported outcomes (EuroQol-5D-5L).

Results

Between May 2021 and July 2025, 31 pts were enrolled. Median age 50 years, M:F-15:16, median PCI=8 at enrollment (range 0-36); PCI 0 n=4, 1-6 n=9, 7-14 n=10, >15 n=8. 98% of pts completed all 4 cycles of protocol treatment. Grade 3 AEs occurred in 15 pts (48.3%). The most common AEs were anemia (n=7; 21.9%), nausea (n=3; 9.4%) and neuropathy (n=3; 9.4%); 11/31 (35.4%) pts underwent CRS (CC-0:100%). In CRS cohort, median PCI at enrollment was 6 (0-24) and at CRS was 1 (0-10). No pts had anastomotic leaks or 30-day readmissions. The PFS12 was 28% (95% CI 0.13:0.46). The median PFS and OS are shown in table.

Conclusions

Iterative normothermic IP PTX plus systemic treatment in GPC is safe and feasible, with encouraging clinical efficacy and safety in historically poor risk patients. The ongoing Phase 2/3 EA2234 STOPGAP II randomized trial will investigate the OS benefit of this approach compared to systemic therapy alone.

Learning Objectives:

To describe the safety and feasibility of Intraperitoneal paclitaxel in gastric carcinomatosis
To describe the selection criteria for cytoreduction in gastric carcinomatosis in a phase II clinical trial
To describe the outcomes of cytoreduction for gastric carcinimatosis in a phase II clinical trial