Influence of induction chemotherapy on target volume and dosimetry of intensity modulated radiotherapy for locally advanced nasopharyngeal carcinoma

As induction chemotherapy goes on, target volume, dose distribution in the surrounding organs at risk (OARs), and target dose conformity all change. Therefore, the question is how to develop reasonable radiotherapy plans in clinical practice. Induction chemotherapy followed by radiotherapy is commonly used around the world, but it is recommended to delineate the target volume based on the gross tumor volume before induction chemotherapy and not to reduce the dose. This point of view lacks the basis of evidence-based medicine. The experts and scholars in China clarify the advantages of radiotherapy plans after induction chemotherapy from the aspects of reducing the target volume, reducing the volume of high-dose region in the target volume, increasing the uniform dose coverage in target volume, reducing dose to OARs, and increasing dose conformity. However, at present, there are no objective data on its long-term efficacy and benefit. Besides, no consensus has been reached on how to delineate the target volume and determine the dose distribution after induction chemotherapy, and further studies are needed. (authors)