De-escalated Radiotherapy for Primary Tumor After Neoadjuvant Therapy With Toripalimab Plus Chemotherapy for Nasopharyngeal Carcinoma

In the IMRT era, patients with stage II-III (AJCC8th) nasopharyngeal carcinoma achieve high local control. However, survivors are increasingly experiencing late radiation-induced toxicities. A previous study found that reducing the radiation dose to the primary site to 60Gy for patients who achieved partial or complete response to induction chemotherapy resulted in a lower rate of late toxicities and an inferior local control rate. The investigators aim to reduce the radiation dose to the primary site for patients after immunochemotherapy, given the potential of neoadjuvant chemotherapy and immunotherapy to increase response rates and long-term survival. The protocol includes participants with stage II-III (AJCC8th), except T2N0M0, to receive three courses of neoadjuvant gemcitabine plus cisplatin and Toripalimab. If the primary tumour regresses by over 75%, de-escalated radiotherapy with 60Gy will be administered, and participants will receive two cycles of cisplatin and three cycles of Toripalimab during the radiotherapy course. Otherwise, participants will receive conventional radiotherapy and concurrent chemotherapy with cisplatin for two cycles as usual. The aim of this study is to investigate the 3-year local control rate and toxicities of de-escalated radiotherapy.