Chemotherapy and Radiation Therapy Practice Test

The key idea is how target volumes are defined to cover not only what is visibly tumor but also disease that isn’t seen on imaging.

The volume that includes potential microscopic disease is the clinical target volume. It extends beyond the visible tumor to cover areas where small numbers of cancer cells could be present, based on tumor type, patterns of spread, and anatomical considerations. This ensures treatment addresses subclinical disease that imaging cannot detect.

In contrast, the gross tumor volume represents only what is clearly visible or measurable, the planning target volume adds margins for daily setup and patient movement, and the internal gross tumor volume accounts for motion of the tumor itself.