Inter-Observer Delineation Differences in Esophageal Cancer GTV on MR, CT, and PET/CT Protokol šečerov Ermenc 28dec19

February 13, 2026 updated by: Institute of Oncology Ljubljana

Inter-observer Delination Variation in Esophageal Cancer Radiotherapy by Use of Magnetic Resonance

Esophageal cancer radiotherapy requires accurate delineation of the gross tumor volume (GTV) to ensure adequate tumor coverage and to minimize radiation dose to surrounding organs at risk. Computed tomography (CT) is routinely used for target delineation, while positron emission tomography-computed tomography (PET/CT) may provide additional functional information. However, uncertainty in tumor boundaries and inter-observer variation remain clinically relevant issues.

Magnetic resonance imaging (MRI) provides improved soft tissue contrast and diffusion-weighted imaging (DWI) information, which may improve visualization of esophageal tumors. This study evaluates whether MRI-based imaging, alone or fused with CT or PET/CT, reduces inter-observer variation in GTV delineation compared with standard CT and PET/CT-based delineation.

A total of 21 patients with locally advanced esophageal cancer undergoing standard radiotherapy preparation will undergo MRI simulation in addition to routine CT and PET/CT simulation. Five experienced radiation oncologists will independently delineate the primary tumor GTV on CT, MRI, PET/CT, CT-MRI fusion, and PET/CT-MRI fusion datasets. Inter-observer variation will be assessed using conformity indices and spatial analysis tools.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Accurate target volume delineation is essential in radiotherapy for esophageal cancer, as contouring uncertainty may lead to geographic miss or increased dose to organs at risk. CT imaging is the standard modality used for radiotherapy planning; however, CT has limited soft tissue contrast, which can make delineation of the proximal and distal tumor extent challenging. PET/CT may assist in staging and may provide functional tumor information, but its value for precise target delineation remains uncertain.

MRI has recently gained importance in radiotherapy planning due to improved anatomical soft tissue visualization and functional imaging such as diffusion-weighted imaging (DWI). Technical advances have improved thoracic MRI feasibility, and MRI may allow improved identification of tumor borders in the esophagus. The clinical role of MRI in reducing inter-observer delineation variability in esophageal cancer radiotherapy planning is not yet well established.

This prospective study compares inter-observer variation in gross tumor volume (GTV) delineation across different imaging modalities used in radiotherapy preparation. Patients with locally advanced esophageal cancer will undergo standard PET/CT simulation according to institutional protocol and additional MRI simulation performed with identical immobilization. MRI will include T2-weighted sequences and DWI sequences without intravenous contrast.

Five experienced radiation oncologists will independently delineate the primary tumor GTV on anonymized datasets using the Eclipse treatment planning system. Contouring will be performed separately on the following image sets: CT, MRI, PET/CT, CT fused with MRI, and PET/CT fused with MRI. Pathologic lymph nodes will not be included in the GTV. A washout period of at least 14 days will be maintained between contouring sessions for the same patient on different imaging modalities.

Inter-observer variation will be assessed using the generalized conformity index (CIgen). Additionally, reference contours will be generated using the STAPLE algorithm. The Contour Analysis Tool (CAT) will be used to calculate planar and volumetric conformity indices (PCI and VCI) and to perform spatial analysis based on inter-delineation distance measurements. Contouring time, image quality, and perceived delineation difficulty will also be recorded by observers.

The primary objective is to determine whether MRI-based imaging reduces inter-observer variability in GTV delineation compared with standard CT and PET/CT imaging in esophageal cancer radiotherapy planning.

Study Type

Interventional

Enrollment (Actual)

23

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 Locations

  • Slovenia
      • Ljubljana, Slovenia, 1000
        • Institute of Oncology Ljubljana

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 ≥18 years
  • Locally advanced esophageal cancer (T1b-4b, N0-N+, M0)
  • Siewert type I or II for distal esophageal tumors
  • Planned preoperative or definitive chemoradiotherapy
  • Written informed consent for participation in the study
  • No contraindications for MRI

Exclusion Criteria:

  • Implanted metallic objects with magnetic properties or electromagnetic devices without MRI compatibility confirmation
  • Physical or psychological conditions preventing informed consent

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: Diagnostic
  • Allocation: Non-Randomized
  • Interventional Model: Factorial Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: CT
Standard planning CT for GTV delineation.
Diagnostic test: Computed Tomography (CT)
CT imaging performed as part of standard radiotherapy simulation and planning for esophageal cancer. CT datasets are used for gross tumor volume (GTV) delineation.
Experimental: MRI
MRI simulation for GTV delineation.
Diagnostic test: Magnetic Resonance Imaging (MRI)
MRI performed on a radiotherapy MRI simulator (T2-weighted sequences and diffusion-weighted imaging) using the same immobilization as CT/PET-CT simulation. MRI datasets are used for GTV delineation.
Active Comparator: PET/CT
PET/CT simulation for GTV delineation.
Diagnostic test: Positron Emission Tomography/Computed Tomography (PET/CT)
FDG PET/CT imaging performed as part of standard radiotherapy preparation. PET/CT datasets are used for GTV delineation, with contouring performed on CT and adjusted using PET information when appropriate.
Experimental: CT + MRI Fusion
CT images fused with MRI for GTV delineation.
Diagnostic test: CT-MRI Image Fusion
Image registration and fusion of MRI with CT datasets for radiotherapy planning. Fused CT-MRI images are used for GTV delineation to evaluate the effect of MRI information on contouring variability.
Experimental: PET/CT + MRI Fusion
PET/CT images fused with MRI for GTV delineation.
Diagnostic test: PET/CT-MRI Image Fusion
Image registration and fusion of MRI with PET/CT datasets for radiotherapy planning. Fused PET/CT-MRI images are used for GTV delineation to evaluate inter-observer variation compared with standard PET/CT-based contouring.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Volumetric Conformity Index (VCI) Compared With Reference Contour
Time Frame: Up to 14 days after completion of contouring for each imaging dataset
Volumetric conformity index (VCI) will be calculated using the Contour Analysis Tool (CAT) by comparing each observer's gross tumor volume (GTV) contour to a reference contour generated using the STAPLE algorithm. VCI is defined as the ratio of intersection volume to union volume and ranges from 0 to 1. The outcome will be reported as mean VCI for each imaging dataset.
Up to 14 days after completion of contouring for each imaging dataset
Inter-observer Variability in GTV Delineation (Generalized Conformity Index, CIgen)
Time Frame: Up to 14 days after completion of contouring for each imaging dataset
Inter-observer agreement in gross tumor volume (GTV) delineation will be assessed using the generalized conformity index (CIgen) calculated using the Contour Analysis Tool (CAT). CIgen is defined as the ratio of the sum of pairwise intersections to the sum of pairwise unions of all observers' contours and ranges from 0 to 1. The outcome will be reported as CIgen for each imaging dataset.
Up to 14 days after completion of contouring for each imaging dataset
Image Quality Rating (5-point Likert Scale)
Time Frame: During contouring sessions (up to 14 days per imaging dataset)
Observers will rate the image quality of each imaging dataset (CT, MRI, PET/CT, CT-MRI fusion, PET/CT-MRI fusion) using a 5-point Likert scale (1 = very poor, 5 = excellent). The outcome will be reported as mean image quality score.
During contouring sessions (up to 14 days per imaging dataset)

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Planar Conformity Index (PCI) Compared With Reference Contour
Time Frame: Up to 14 days after completion of contouring for each imaging dataset
Planar conformity index (PCI) will be calculated using the Contour Analysis Tool (CAT) by comparing each observer's GTV contour to a reference contour generated using the STAPLE algorithm. PCI is defined as the ratio of intersection area to union area and ranges from 0 to 1. The outcome will be reported as mean PCI for each imaging dataset.
Up to 14 days after completion of contouring for each imaging dataset
Spatial Inter-delineation Distance (IDD) Between Observer Contours and Reference Contour
Time Frame: Up to 14 days after completion of contouring for each imaging dataset
Inter-delineation distance (IDD) will be calculated using the Contour Analysis Tool (CAT) as the shortest distance between each observer's GTV contour and the reference contour, expressed in millimeters (mm). The outcome will be reported as mean IDD (mm) for each imaging dataset.
Up to 14 days after completion of contouring for each imaging dataset
Contouring Time
Time Frame: During contouring sessions (up to 14 days per imaging dataset)
Time required for gross tumor volume (GTV) delineation will be recorded for each observer and imaging dataset and reported in minutes.
During contouring sessions (up to 14 days per imaging dataset)
Perceived Difficulty of Delineation (5-point Likert Scale)
Time Frame: During contouring sessions (up to 14 days per imaging dataset)
Observers will rate the perceived difficulty of GTV delineation for each imaging dataset using a 5-point Likert scale (1 = very easy, 5 = very difficult). The outcome will be reported as mean difficulty score.
During contouring sessions (up to 14 days per imaging dataset)

Collaborators and Investigators

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

Sponsor

Institute of Oncology Ljubljana

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)

January 1, 2020

Primary Completion (Actual)

June 30, 2021

Study Completion (Actual)

June 30, 2021

Study Registration Dates

First Submitted

February 6, 2026

First Submitted That Met QC Criteria

February 13, 2026

First Posted (Actual)

February 18, 2026

Study Record Updates

Last Update Posted (Actual)

February 18, 2026

Last Update Submitted That Met QC Criteria

February 13, 2026

Last Verified

February 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • ERID-KSOPKR-0005/2020
  • ARRS / ID: 33071 (Other Identifier: Slovenian Research Agency (ARRS))

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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