PULSAR Combined With Immunotherapy for Unresectable Locally Advanced Gastric Cancer

May 24, 2026 updated by: Jeong Il Yu, Samsung Medical Center

A Prospective Phase II Study of Systemic Therapy With Immunotherapy Combined With Personalized Ultrafractionated Stereotactic Adaptive Radiation Therapy (PULSAR) in Unresectable Locally Advanced Gastric Cancer

The purpose of this prospective, single-center, phase II study is to evaluate the clinical efficacy and safety of combining first-line systemic therapy plus immunotherapy with personalized ultrafractionated stereotactic adaptive radiation therapy (PULSAR) in patients with unresectable locally advanced gastric cancer.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

Standard first-line treatment for unresectable locally advanced gastric cancer is systemic chemotherapy combined with immunotherapy, but the overall prognosis remains poor, and local complications like bleeding or obstruction frequently occur.

ULSAR delivers a high dose of radiation per fraction using a 3-to-4 week interval. This extended fraction interval allows normal tissue recovery and provides an opportunity for adaptive replanning before each fraction to minimize gastrointestinal toxicities while maximizing tumor dose delivery. Furthermore, this unique scheduling allows seamless integration with systemic immunotherapy without interrupting the regular chemotherapy cycle. This study specifically aims to evaluate if PULSAR can improve local control, conversion to surgery, and progression-free survival in HER-2 negative, EBV negative, and MSS gastric cancer patients whose tumors have not progressed after at least 3 cycles of first-line immunotherapy-containing systemic regimens.

Study Type

Interventional

Enrollment (Estimated)

53

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • South Korea
    • Select Province/State
      • Seoul, Select Province/State, South Korea, 06351
        • Recruiting
        • Samsung Medical Center
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

Age 19 or more years. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0-2. Histologically confirmed gastric adenocarcinoma. Tumor biomarker status: HER-2 negative, EBV negative, and Microsatellite Stable (MSS).

Unresectable, locally advanced extent at initial staging (Para-aortic lymph node [PALN] and Supraclavicular lymph node [SCN] metastases are allowed).

Has completed 3 or more cycles of first-line systemic therapy combined with immunotherapy without evidence of disease progression.

Presence of at least one evaluable lesion according to RECIST v1.1 that is deemed safely irradiable by the investigator.

Voluntary written informed consent provided by the subject.

Exclusion Criteria:

Pregnant or lactating women. Presence of brain metastases or leptomeningeal involvement. Prior history of radiation therapy to the intended target site. Severe uncontrolled comorbidities that, in the investigator's opinion, limit study participation or treatment compliance (e.g., uncontrolled infection, heart failure, arrhythmia, psychiatric illness).

Inability or unwillingness to comply with the study protocol procedures. Any condition deemed inappropriate for study participation by the principal investigator or attending physician.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Experimental Group (PULSAR + Immunotherapy)
Patients with unresectable locally advanced gastric cancer who did not progress after 3 or more cycles of first-line immunotherapy-containing systemic therapy will receive personalized ultrafractionated stereotactic adaptive radiation therapy (PULSAR)
Radiation: PULSAR (Personalized Ultrafractionated Stereotactic Adaptive Radiation Therapy)
Dose Schedule: 6 Gy per fraction administered every 3-4 weeks
Radiation: PULSAR
Administer a single dose of 6 Gy of radiation, up to a total of 3 cycles, at 3-4 week intervals, along with standard systemic therapy.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Progression-Free Survival (PFS) Rate at 12 Months
Time Frame: PFS at 12 months, calculated from the end date of the 1st PULSAR fraction.
Defined as the percentage of patients alive without any evidence of disease progression per RECIST v1.1 at 12 months, calculated from the end date of the 1st PULSAR fraction.
PFS at 12 months, calculated from the end date of the 1st PULSAR fraction.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Samsung Medical Center

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

May 15, 2026

Primary Completion (Estimated)

April 30, 2028

Study Completion (Estimated)

April 30, 2030

Study Registration Dates

First Submitted

May 19, 2026

First Submitted That Met QC Criteria

May 19, 2026

First Posted (Actual)

May 26, 2026

Study Record Updates

Last Update Posted (Actual)

May 28, 2026

Last Update Submitted That Met QC Criteria

May 24, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • PULSAR-GC-1.2

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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