What is the significance of the dose-volume histogram (DVH) in radiotherapy planning?

• A. It quantifies dose distribution to target and organs at risk to meet constraints and minimize toxicity
• B. It measures tumor size
• C. It determines chemotherapy schedule
• D. It predicts patient comfort

Answer: (A)

DVH is a tool that translates the three‑dimensional dose distribution into simple curves for each structure, showing what fraction or what volume of that structure receives at least a given dose. This is crucial because the goal of radiotherapy planning is to deliver the prescribed dose to the target while keeping doses to nearby organs at risk within safe limits. The DVH lets you confirm that the target is adequately covered (for example, ensuring the prescription dose reaches most of the target) and that organs at risk stay below their tolerance thresholds. By comparing DVHs from different plan options, you can adjust beam arrangements, weights, and modulation to maximize tumor control while minimizing toxicity. The DVH reflects dose distribution, not tumor size from imaging, and it doesn’t determine chemotherapy schedules or directly predict patient comfort, though a well-optimized DVH contributes to safer, more tolerable treatment.