Skip to main content
OpenTrials
Not yet recruiting

NCT Number: NCT07818798

Proton and Proton-Photon Hybrid Partial Stereotactic Ablative Boost Radiotherapy (P-SABR) for Unresectable Large Tumors

This prospective, multicenter, observational cohort study will enroll 60 adults with unresectable larege tumors (longest diameter > 5 cm) who receive one of two treatment modes: (A) proton P-SABR, in which both the proton partial-SABR boost (course 1) and the subsequent proton CFRT (course 2) are delivered at the proton center; or (B) proton-photon hybrid P-SABR, in which course 1 is delivered with protons at the proton center and course 2 CFRT is delivered with photons. The primary objective is to describe, in each cohort, the incidence of treatment-related grade ≥ 3 acute and late adverse events (CTCAE v5.0). Secondary objectives are dosimetric and the 1-year local control rate (RECIST 1.1, in-field). Participants are followed for up to 5 years.

Not yet recruiting

Trial opening soon.

Get Notified

Key information

Conditions

Unresectable Malignant Neoplasm Bulky Tumor Solid Tumor

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

About this study

BACKGROUND Large tumors (longest diameter > 5 cm) are often unresectable and respond poorly to conventionally fractionated radiotherapy (CFRT) because of their size and hypoxic core, while normal-tissue tolerance prevents delivering stereotactic ablative radiotherapy (SABR) to the whole tumor. Partial stereotactic ablative boost radiotherapy (P-SABR) delivers a SABR boost only to the central part of a large tumor, followed by CFRT to the whole target. Proton beams, with their Bragg-peak dose fall-off, may sharpen this "onion-skin" dose distribution and further increase the biologically effective dose (BED) within the tumor core.

DESIGN This prospective, multicenter, observational cohort study will enroll 60 adults with unresectable bulky tumors (longest diameter > 5 cm) who, as part of routine care, receive one of two treatment modes: (A) proton P-SABR, in which both the proton partial-SABR boost (course 1) and the subsequent proton CFRT (course 2) are delivered at the proton center; or (B) proton-photon hybrid P-SABR, in which course 1 is delivered with protons at the proton center and course 2 CFRT is delivered with photons (IMRT/VMAT) either at the same center or at Peking University First Hospital or one of six photon sub-centers, after central review of the composite plan. Cohort membership follows the patient's own choice and care pathway; the study does not assign treatment or intervene in clinical decisions, and no formal between-cohort hypothesis testing is planned.

OUTCOMES The primary objective is to describe, in each cohort, the incidence of treatment-related grade ≥ 3 acute and late adverse events (CTCAE v5.0). Secondary objectives are dosimetric (percentage of the GTV receiving BED10 ≥ 100 Gy, PTV V95% and V100%, organ-at-risk doses) and the 1-year local control rate (RECIST 1.1, in-field). Participants are followed for up to 5 years.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Histologically or cytologically confirmed malignancy
  • At least one tumor with a longest diameter > 5 cm
  • Not amenable to curative surgical resection, or patient declines surgery, or surgery contraindicated because of medical comorbidities
  • Age ≥ 18 years
  • ECOG performance status 0-2
  • Life expectancy > 3 months
  • Written informed consent

Exclusion criteria

  • Prior radiotherapy to the same site
  • Severe cardiopulmonary insufficiency precluding radiotherapy
  • Concurrent other active malignancy
  • Uncontrolled acute infection or bowel obstruction
  • Pregnancy or breastfeeding
  • Intracranial lesion
  • Tumor directly invading the full thickness of the esophageal, gastric or intestinal wall with active ulceration, fistula or uncontrolled risk of perforation (tumors that only abut or displace a hollow organ without full-thickness invasion are not excluded)
  • Uncontrolled active tumor bleeding, or impending pathological fracture requiring orthopedic intervention
  • Any other condition that, in the investigator's judgment, makes the patient unsuitable for the study

Treatment and study plan

Proton P-SABR

Radiation

Course 1 (proton partial-SABR boost, IMPT): CTV 1.8-3 Gy per fraction with a simultaneous boost to the boost volume within the GTV (GTVb) of 8 Gy × 3 fractions; in larger tumors the inner GTVb (GTVb shrunk by 1 cm) is further boosted to 12 Gy × 3 fractions; critical organs at risk < 3 Gy per fraction; robust optimization on the CTV. Course 2 (proton CFRT): CTV 1.8-3 Gy per fraction with robust optimization, to a cumulative PTV dose of 60-70 Gy on the summed plan, with GTVb BED10 ≥ 100 Gy. Proton dose is expressed with a constant RBE of 1.1. Both courses are delivered at Hebei Yizhou Cancer Hospital.

Other names: Proton partial stereotactic ablative boost radiotherapy, Proton partial-SABR boost followed by proton conventionally fractionated radiotherapy

Proton-Photon Hybrid P-SABR

Radiation

Course 1 identical to Cohort A: proton partial-SABR boost (IMPT) with GTVb 8 Gy × 3 fractions and inner GTVb 12 Gy × 3 fractions, delivered at Hebei Yizhou Cancer Hospital. Course 2 (photon CFRT): IMRT/VMAT with daily CBCT recommended, PTV 1.8-3 Gy per fraction to a cumulative PTV dose of 60-70 Gy on the summed plan, with GTVb BED10 ≥ 100 Gy, delivered at Hebei Yizhou Cancer Hospital (same-center) or at Peking University First Hospital or a photon sub-center (cross-center). For cross-center participants, DICOM-RT structure, plan and dose files of both courses are reviewed by the central radiotherapy QA committee, which performs deformable registration and dose summation (MIM; proton RBE = 1.1) before course 2 starts. Target interval between courses ≤ 3 working days (maximum 7 working days).

Other names: Proton-photon hybrid partial stereotactic ablative boost radiotherapy, Proton partial-SABR boost followed by photon conventionally fractionated radiotherapy

Primary outcomes

  1. Incidence of treatment-related adverse events of grade ≥ 3 (CTCAE v5.0)

    Time frame: From the first fraction of radiotherapy to the end of the study

    Up to 5 years after completion of radiotherapy (acute events: from the first fraction of radiotherapy through 90 days after completion; late events: from day 91 after completion through 5 years)

Secondary outcomes

  1. Percentage of the gross tumor volume (GTV) receiving a biologically effective dose (BED10) ≥ 100 Gy

    Time frame: Up to 3 weeks after the first fraction of radiotherapy (when the composite plan of course 1 and course 2 is finalized)

    Volume fraction (%) of the GTV receiving BED10 ≥ 100 Gy on the composite (summed) plan, extracted from the treatment planning system (proton dose converted with RBE = 1.1; dose summation in MIM ).

  2. Planning target volume (PTV) coverage: V95% and V100%

    Time frame: Up to 3 weeks after the first fraction of radiotherapy (when the composite plan of course 1 and course 2 is finalized)

    Percentage of the PTV receiving ≥ 95% (V95%) and ≥ 100% (V100%) of the prescribed cumulative dose on the composite plan, reported per cohort as mean ± SD.

  3. Doses to organs at risk (OARs)

    Time frame: Up to 3 weeks after the first fraction of radiotherapy (when the composite plan of course 1 and course 2 is finalized)

    Dose metrics of organs at risk (e.g., spinal cord maximum dose, esophagus, lung, bowel, brachial plexus) on the composite plan, and the proportion of participants meeting each OAR dose constraint, reported per OAR and per cohort with 95% CI.

  4. 1-year local control (LC) rate

    Time frame: 12 months after the first fraction of radiotherapy

    Local control is defined as the absence of progressive disease (RECIST 1.1) in in-field lesions; the in-field region is defined by the GTV/CTV/PTV projections exported from the treatment planning system (DICOM-RT) and confirmed by blinded central imaging review. Time to local progression is measured from the first fraction of radiotherapy. The 1-year LC rate and its Greenwood 95% CI are estimated per cohort with the Kaplan-Meier method; no between-cohort test is performed.

Interested in participating?

Not yet recruiting

Trial opening soon.

Get Notified

Sponsors and collaborators

Lead sponsor

Peking University First Hospital

Other

Registry information

Official study title

A Prospective, Multicenter, Observational Cohort Study of Proton and Proton-Photon Hybrid Partial Stereotactic Ablative Boost Radiotherapy (P-SABR) for Unresectable Large Tumors

Acronym: LARGE-Proton

Important dates

Study start
2026
Primary completion
2029
Study completion
2029
First posted
Sep 14, 2026
Registry last updated
Sep 14, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

Related clinical trials

Published trials that share one or more normalized conditions with this study.