CTV Delineation Based Solely on Geometric Expansion From GTV in Nasopharyngeal Carcinoma

All enrolled patients underwent intensity-modulated radiation therapy (IMRT). The IMRT technique was selected based on the equipment available at each treatment center and the patients' preferences, including IMRT, VMAT, or TOMOTHERAPY. According to our study design, all enrolled patients will be randomly assigned in a 1:1 ratio before radiation therapy. The target area definitions are based on the international ICRU reports No. 50 and No. 60. The specific target area definitions and prescribed doses for the two groups are as follows:

• GTVp (70Gy/33Fx) Experimental Group: Gross tumor as seen on imaging and nasopharyngoscopy; Control Group: Gross tumor as seen on imaging and nasopharyngoscopy.
• CTVp1 (60Gy/33Fx) Experimental Group: None; Control Group: GTVp + 5 mm + entire nasopharyngeal mucosa.
• CTVp2 (54Gy/33Fx) Experimental Group: GTVp + 10 mm + entire nasopharyngeal mucosa; Control Group: GTVp + 10 mm + high-risk anatomical structures.
• GTVn Experimental Group: Lymph nodes as seen on imaging; Control Group: Lymph nodes as seen on imaging.
• CTVn Experimental Group: Defined according to CACA/CMDA guidelines; Control Group: Defined according to CACA/CMDA guidelines.

Inclusion criteria

• Pathologic diagnosis (pathologically confirmed by nasopharyngeal biopsy) was nasopharyngeal carcinoma;
• No distant metastatic;
• Patients with baseline MRI date of nasopharynx and neck, and completed the first course of treatment in our hospital;
• Eastern Cooperative Oncology Group (ECOG) score of 0 or 1;
• Signing informed consent;
• Follow up regularly and comply with test requirements.

Exclusion criteria

• Disease progression during IMRT;
• Previous malignancy or other concomitant malignant diseases;
• The evaluation information of tumor efficacy can not be obtained;
• Receive blind treatment in other clinical research;
• Have or are suffering from other malignant tumors within 5 years (except non- melanoma skin cancer or pre-invasive cervical cancer);
• Serious complications, such as uncontrolled hypertension, coronary heart disease, diabetes, heart failure, etc;
• Active systemic infection;
• No or limited capacity for civil conduct;
• The patient has a physical or mental disorder, and the researcher considers that the patient is unable to fully or fully understand the possible complications of this study;
• Pregnancy or lactation period;