**3. Definition of high risk clinical target volume (HR‐CTV)**

The most important target volume in IGABT, the HR‐CTV, can be defined at the time of first BT. In the recommendations from the GYN GEO‐ESTRO working group, a brief definition of HR‐ CTV in 3D image-based 3D treatment is described as follows (1) carrying a high tumor load, includes the gross tumor volume (GTV) and always includes the whole cervix and presumed extracervical tumor extension at the time of BT. Limited disease is defined as a tumor less than 4 cm and/or limited to the cervix at the time of diagnosis. Therefore, in such cases, the whole cervix including the GTV at BT corresponds to the HR-CTV. For extensive disease, presumed tumor extension is defined by clinical examination (visualization and palpation) and imaging (MRI). Interstitial needles are usually required in such extensive cases. Examples of HR-CTVs of both limited and extensive cases treated at Kobe University are shown in **Figures 1** and **2**.

**Figure 1.** HR-CTV (pink and outer line) and GTV (red and inner line) of limited disease delineated on axial image (original) and coronal image (reconstructed).

**Figure 2.** HR-CTV (pink and outer line) and GTV (red and inner line) of extensive disease delineated on axial image (original) and coronal image (reconstructed).
