Measurement of lung tumor volumes using three-dimensional computer planning software

Area of Science:

• Radiation Oncology
• Medical Imaging
• Oncology

Background:

• Accurate delineation of Gross Tumor Volume (GTV) is crucial for effective radiotherapy planning in non-small-cell lung cancer (NSCLC).
• Interclinician variability in GTV contouring can lead to inconsistencies in radiation dose delivery and treatment outcomes.

Purpose of the Study:

• To quantify interclinician variation in GTV definition for NSCLC patients undergoing radiotherapy.
• To develop and evaluate methods for minimizing this variation.
• To test the efficacy of a revised protocol in standardizing GTV delineation.

Main Methods:

• Six oncologists independently contoured GTVs on CT scans of 6 NSCLC patients, guided by radiologist markings.
• Contouring was performed using both mediastinal and lung window settings.
• A revised protocol was implemented after 3 years, and 5 clinicians re-contoured GTVs to assess variation reduction.

Main Results:

• Initial GTV volume measurements showed significant interclinician variation, ranging from 5% to 42% (average 20%).
• Reasons for variation included inclusion of low-probability tumor regions, adjacent atelectasis, and inconsistent spicule treatment.
• The revised protocol reduced variation to 7-22% (average 13%), with non-statistically significant differences among clinicians.

Conclusions:

• Significant variation exists in the 3D GTV delineation of NSCLC among oncologists, despite radiologic guidance.
• Standardization through a revised protocol effectively reduced interclinician variation.
• Implementing standardized guidelines is essential for improving consistency in NSCLC radiotherapy planning.