What is the clinical target volume?

The clinical target volume (CTV) is defined as the volume that encompasses the tumor as well as the surrounding tissue that may contain microscopic disease. Its purpose is to ensure that all potential disease sites are encompassed during treatment planning, acknowledging that cancer cells can extend beyond the visible or palpable tumor itself. This is why the CTV is considered larger than the tumor volume. The inclusion of surrounding tissues accounts for the uncertainty related to the exact extent of the disease, which may not be detectable using medical imaging. Therefore, the relationship between the CTV and the tumor volume is such that the CTV must encompass the tumor and any potential areas of involvement to ensure effective treatment coverage.