Interobserver Variability in Contouring Hepatocellular Carcinoma at a Tertiary Center

Area of Science:

• Radiology
• Oncology
• Medical Imaging

Background:

• Optimal imaging for hepatocellular carcinoma (HCC) gross tumor volume (GTV) delineation in radiotherapy remains undefined.
• Magnetic resonance imaging (MRI) is hypothesized to offer superior visualization compared to computed tomography (CT).

Purpose of the Study:

• To compare the accuracy of GTV delineation for liver stereotactic radiotherapy using MRI versus CT.
• To evaluate interobserver agreement in GTV delineation of HCC.

Main Methods:

• Eight radiation oncologists delineated GTVs from CT and MRI scans of five HCC patients.
• GTV volumes and interobserver variability were compared between CT and MRI datasets.

Main Results:

• Median GTV volume on MRI (2.4 cm³) was not significantly different from CT (3.5 cm³).
• MRI delineated larger or equal GTV volumes in two cases.
• Interobserver variance and standard deviation were minor for both CT and MRI.

Conclusions:

• CT is reproducible for well-defined HCC tumors.
• MRI can be a complementary tool when CT delineation is unclear.
• Significant interobserver variability in HCC target delineation warrants attention.